THE PROFESSOR SERIES PART 1A

Author: ianlt
Title: THE PROFESSOR SERIES: PART IA
Date: 10 October 2015

This story is not the kind of story with lots of BDSM and sex. (I promise those are here in the story though) It is a mixture of relationship based story telling, as well as sume musings about "lether" relationships, and even theology. I wouldn't want to disappoint those who might not be interested in my philosophical meanderings, so forewarned, is warned! :)


THE PROFESSOR SERIES: PART IA


For a man like me, I have the best job. I teach college writing at a college known not for its academics but rather for its location on one of the best beaches in California. It attracts the kind of students which makes my cock hard; lean, tanned, sunbleached, beautiful men. Given the academic climate, most of these students end up in College Writing rather than testing out of it. I make a point of teaching that class. Given my charisma the young women clamor to get in my class, so the men follow.
My charisma? I have a rebel, hard image. I’m a leatherman. It is just that these beach kids don’t have a clue what it really means, nor is it necessary for them to know. My “clean biker” look is just cool to them. So I ride my Harley, wear high thick black leather boots, my tight black leather pants to lecture and wear a black leather vest over my T-shirt. Silver hair just past the nape of my neck, and a goatee. I’ve got a great body that I work hard to maintain, lean and muscular, tanned with enough 50 something wrinkles to make my face interesting, steel blue eyes, and a thick steel hoop in my left ear. I’m known as a hard but fair professor who teaches an interesting class.
“Hard but fair” explains my relationship with the water polo team. The other thing this school is known for is water polo. The team is excellent. The coach likes boys who surf because of their great stamina, upper body strength, and comfort in the water. Surfing is highly encouraged. Needless to say, we get a great crop of players each year, nearly all of who end up in my class. If they don’t pass, they don’t play. The coach has long since accepted that there are no special breaks for his team. So we have become good friends and I like to spend my afternoons watching practice after my own workout at the gym.
Half way through the quarter I was sitting there watching the end of polo practice. As they were hopping out of the pool, joshing, playfully shoving each other, knocking the balls off each other’s bodies, Dave Tucker separated himself from the group and approached me. As he did so, he pulled off his cap and shook out his shoulder length gold, bleached white hair. He toweled his crotch, lifting it, all the while looking straight at me with a nervous but seductive smile. God, he was beautiful. A truly perfect specimen; tall, 6’ 3” or so, lean but with muscles draped over his body, a broad chest, narrow waist and hips, tight ass, washboard abs, darkly tanned with sunburned nose and perfect teeth. My cock rose to greet him as I stood up.
His provocative approach was unusual but his story however was the usual one. He was enrolled in my 8 AM class and between surfing with his buddies on the best morning waves, or partying too much the night before to get up for class, he had missed the majority of my classes. Needless to say, he was failing on the mid term report required for freshman athletes. As he stood there, he gave me the usual excuses and pleading. I replied with a restatement of my class standards and a firm “no”. The conversation was far too typical.
Then he rearranged his body position and ran his hand through his hair. He was suddenly nervous in that cocky macho sort of way that I just love in these young jocks. I could tell his throat was dry as he stammered out a question.
“Look, Dr. Lewis, I need to be passing. What if I, well, what if I fuck you, or maybe let you fuck me?”
The question was rushed, mumbled and drifted away at the end. I was astonished but had enough presence of mind to surreptitiously reach into my vest pocket and switch to “record” the recording device I had been using during the practice for notes and reminders. With the volume turned up, I asked him to repeat his question.
He shifted his feet, looked in my eyes with more confidence and with a sexy smile asked, “I can’t play unless I’m passing your class. The tournament is coming up and they need me. I have to play. So look, if I, I mean, will you fix my grade if I fuck you, or if you would rather, if I let you fuck me? Sir?” This time the question came out more clearly.
I took a deep breath and thought quickly.
I kept my hand in the pocket with the device and replied, “Mr. Tucker, This is hardly the place, on the college campus, to be asking me that kind of question. As a faculty member of this college I reject your request. In fact I should turn you in.”
Quickly I switched off the recorder and spoke quickly to break over his coming protest. I smiled back at him.
“Notice that I said that your question was inappropriate on the college campus and that I should, but not necessarily, would, turn you in. Tomorrow is Saturday, get your surfing done and be at my house at eleven o’clock. We will discuss the appropriate response to your question at that time.”
“Now go, get dressed and go home.”
I watched him turn and go. Clearly, he was confused by my reply, wondering if I said yes or if I was going to have him expelled. I just laughed.


My house is a two story 100 year old Craftsman style bungalow on one of those narrow side streets that end in the sand. It is light, and airy, the large wide windows open, the perfect old house on the beach. I lounged back on a porch chair, my feet up on the railing. For the occasion of the 11 AM visit, I had on my tallest boots, and tightest chaps over my faded jeans. No shirt, just my vest and leather armbands. It was a great sunny day, already hot in the sun. I suppose I should have wondered if he would show up, but I believed he was aware how much power he had given to me. I expected him to show up.
Friday afternoon after our conversation, I found that David Tucker was a scholarship polo player but he didn’t need it. His home was in Palos Verdes where even the shacks, if there were any, would cost a couple million dollars. His transcripts indicated his test scores were quite high in spite of rather poor grades and absences at school. His references commented on his more than adequate intelligence, but, also, that he cared more for the surf and water polo than academics.
At ten minutes after 11, a Kawasaki motorcycle turned onto my street. It was black with gold trim. The rider was mounted atop, hugging the huge body of the machine. A true phallic symbol. The rider was in a black leather racing suit with a full head black helmet and darkened visor. As much as I found this black combination of man and machine wildly erotic, I was annoyed as it stopped in front of my house and the rider climbed off. I didn’t need company, no matter who it was, just as I was expecting Mr. Tucker.
Then I recognized the golden hair between the collar and the helmet. Will wonders never cease; this Mr. Tucker is full of surprises. Some assumptions I made last night were reinforced.
He took off his helmet and ran his hand through his hair adjusting his crotch at the same time. There was no seductive intention in this gesture this time. My crotch enlarged.
“Dr Lewis,” he began.
I stopped him and firmly told him that this meeting would be more productive if he made no further attempts at excuses and only truthfully answered my questions.
He looked down and said, “Yes Sir.” My cocked throbbed in its cock ring.
Now Mr. Tucker,” I began, “I have no intention to fuck you, or to be fucked by you as you are a student of mine. That would be highly unethical especially as it was offered as a bribe. Do you understand?”
Eyes cast down, and incredibly, his hands behind his back, his helmet tucked under his arm, he replied, “Yes Sir.”
“Then come in the house, and we will discuss your behavior and the proper response I should take.” I said this and turned off the transcription device again. He followed me into the living room and sat on the edge of one of my huge chairs while I got us some lemonade. From the kitchen I could observe him. Oh God, he was beautiful. In full black leathers no less. Rather different attire from most students especially as the day was getting hot. He was nervously glancing around now that I was out of the room. He unzipped his jacket some, and ran his hands through his hair, then settled into a pose of casual indifference awaiting my return. A gold chain was around his neck and he had no shirt on underneath his leathers.
He had the presence of mind to thank me for the glass.
“You have a beautiful bike, Mr. Tucker.” I began. I began a casual conversation in which his part was to answer my questions. His casual indifference was wearing thin. So it was time to begin.
“Mr. Tucker,” I began, “I understand your concern about your status in my class. Believe it or not, I even understand why you got yourself into this situation. I have heard from you all the standard pleading and excuses. Sometimes I believe they teach a course on this as part of orientation. But what interests me is the ‘why’ behind the offer you made to me. Why did you ask it?”
“Dr. Lewis, I’m sorry. I didn’t mean it.”
“Mr. Tucker, may I remind you that excuses and dishonest apologies are not conducive to this conversation. You made me an unusual offer, os I repeat, why did you do so?”
“I don’t know. I was just desperate.”
“I’m sure you do know, even as I acknowledge that you were desperate. But you offered, in exchange for a passing grade to either fuck me, or to be fucked by me. What led you to believe that such an offer would be of interest to me?”
He was now clearly uncomfortable. Running his hands through his hair was now a nervous gesture. He was sweating but didn’t unzip his jacket any further. I was delighted.
“I don’t know, nothing, I guess, Christ, Dr. Lewis, can’t we just forget this?”
“No, Mr. Tucker. It is instinctually obvious that a negotiator leaves his best and most powerful offer as his final one. I expect to know the basis of that offer.”
He ran his hand under his tall collar. “Well, you know, I mean, I’ve heard that it might interest you, and all.”
“Really, and from what source did such a rumor come?”
“Oh God, Dr Lewis, I’m sorry, I had just heard something and I was desperate. I wasn’t implying anything. I’m sorry, I just heard it and thought well, maybe this would work.”
“Of course, you were implying something, by making me that offer. If you would show up to class, you would have some grasp of basic logic. You were implying that I’m a gay man, and I expect to hear from you the source of this assumption.”
My sexual activities have always been my private affair. A leatherman would recognize me if he saw me. I just see no need to make a deal of my sexual orientation around this town and college. And my sexual orientation is exclusively, first and foremost a leather top. I’m posted on some highly graphic web listings. I’m a successful author under a pseudonym (how else could I have afforded this house) and I’m quite well known at the leather clubs in the city 50 miles to the south. In fact I was at my favorite last night and will be there tomorrow afternoon as well. For someone to know that I am a leatherman and what that meant, he would have to be seriously into leather, or at least be seriously interested in learning about it.
“Well I just heard you might be, I mean it is cool and everything. The babes would be disappointed in your classes but it’s cool”
“Again, Mr. Dawson, You are not answering my question.”
“Well, I went into a bar, a bar in the city, a gay bar on a dare from a friend, and, I’m sorry, and I saw you there.”
“Try again, Mr. Dawson” I said. “I don’t frequent bars.” Admittedly I am being legalistic here. My club serves beer. But it also has a strict dress code, one has to be a guest or a member, and the club is unmarked, so one can’t stumble into it by accident.
“But I saw you there,” he protested, then he caught himself, “well, maybe I was mistaken.”
He comes into my house wearing leather. He saw me at a ‘bar.’ The only way he could have been there would have been for him to be highly motivated to find it. My cock is now aching in the confines of my jeans.
“Tell me, Mr. Tucker,” I ask, “Would you like to fuck me, or would you like me to fuck you?”
“God no, I mean it is cool and everything, but I’m straight. Neither way, man, I mean, I was just desperate for the class.”
“You know something, Mr. Dawson, I believe that you are being less than honest with me and I expect truthfulness.” I pulled the recording device from my pocket and pushed the rewind button. His eyes opened wide and he swore and put his hands through his hair once again. I was beginning to find that gesture endearing.
I pushed play, and the final comments of my work yesterday at the poolside were heard. This was followed by his offer of sex in exchange for a grade followed by my double refusals.
“Oh shit,” he swore. He wasn’t angry as I expected he might become. Instead he visibly sagged, repeated my now favorite gesture and said to himself, “I’m screwed”
The sadist in me caused me to say, “I thought you didn’t want to be fucked?” Part of me wanted to hold him in my arms and comfort him, but that would have to wait.
“You recognize that this tape, if I turn it in, will get you expelled, and will, if the coach hears it, prevent you from ever playing water polo again anywhere.”
“Yes,” he replied quietly, “What are you going to do.”
“I haven’t decided yet,” I replied. “First I need to do an experiment on you. I expect you will cooperate?”
“I guess I have no choice,” he replied warily. “What kind of experiment? What are you going to do?”
“Of course you have a choice but there are always consequences to a choice. I have a theory that I want to test. You will have to trust me.”
He was nervous but resigned. When I brought out the leather cuffs, padlocks and chains, all of which I had in the drawer next to where I was sitting, it was obvious that he was ready to run, but also I thought I saw a look of abject desire in his eyes.
“Put these cuffs on,” I said. He knew what to do with them, another confirmation of my suspicion. He held his arms out while I buckled the wrist cuffs, and he put his boot on my knee as I cuffed his ankles. “Get your helmet and follow me,” I ordered. I turned and walked away and he followed.
I led him to my backyard. There is a high fence, which provides privacy and also stops the ocean breezes. When it is too cool to be on the beach the yard is a great place to sit in the sun. It gets too hot on a warm sunny day to be comfortable and the day was a warm sunny day. In the center of the yard is a concrete patio, which just so happens to have 4 eyehooks embedded into the concrete.
I told him to lie down on his back. I could tell his heart was racing. He knew what was going to happen and he was allowing it. I used the chain and padlocks to spread-eagle him on the concrete. He was going nowhere. He said nothing. He could have easily called for help. I used black duct tape to tape his mouth shut, covering his lower face, and then taped his eyes closed before I place the helmet on his head and shut the visor. I zipped up his collar and then reached down to assess the outcome of my experiment.
I unzipped his pants and found no underwear. However he had a leather cockring on and his cock was hugely erect. My suspicions were amply confirmed and my experiment was a huge success.
I left him to get warm, a huge understatement actually. I put in a call to my club. I described Dave to the owner. If Dave had tried to get in, the owner would know. No one would forget a beauty like him. And my suspicions were confirmed once again. The owner recalled letting in a young man that fit the description a week back. “A favor to the members, really” he said as an explanation for letting an underage non-member enter. It was a Friday night. I would have been there but I must have been preoccupied. The owner said that the young man was quite nervous and only stayed a couple moments before he left, much to the disappointment of all the guys that saw him. I told the owner that that very same young man was chained and lying in my backyard at the very moment. I was wished the most sincere luck.
Anything more than an hour, enclosed in his black leather, spread out in the full sun would have killed him. During that time I would glance out the window, and his cock remained thick and sticking straight up. It was time for step two. I unzipped his jacket and pants. I heard a muffled sigh of relief. He was drenched, pools of water on his body. I placed titclamps just behind the tips of his tits. He groaned and struggled briefly, but his cock got even harder. I tweaked his tits and his cock a few times and he flinched. I put a ball stretcher on him followed by a parachute harness. I tied the end of a cord to the parachute, pulled tightly till he groaned and tied the cord off around the soles of his boots. This pulled his upright cock to angle down to his feet. So I tied a leather cord around his cock. He bucked like he was about to cum as I worked on his cock. The head of his cock was huge, red and gapping. I tied the end of the cord, which was knotted at the head of his cock to the tit clamp chain, which straightened his cock back to straight up. He was making sounds and squirming.
I took off his helmet. His hair was as wet as if he had just climbed out of the surf. I pulled off the tape, none too gently. He swore in both pain and pleasure and said “Thank you.”
I held his head up and told him too look at himself. He didn’t say anything but he seemed pleased. Then I gave him a large glass of lemonade to drink, holding his head to help him drink. He kept mumbling “Thank you.”
I knelt over him, straddling his trunk. He flinched as my body pulled the cord between his cock and tits. “Now, Mr. Tucker, let us begin our conversation again.”
As we talked, I gently massaged his tits. I could feel him bucking in ecstasy beneath me. In fact I got his whole sexual life story from him. He had tied himself up since he was a little kid. He sometimes got his surfing buds to play tie up games, but not often. His first orgasm came when he had tied himself up, and since then whenever he could, he would repeat the experience. Instead of getting the usual red or yellow motorcycle he got a black one and the black leathers and boots to go with it. His friends thought he was a wimp for wearing racing leathers rather than the more standard uniform of just shorts, track shoes and helmet. He loved putting the leather on. When he turned 16 he would cycle up to West Hollywood and hang out looking at the men. He guessed he had been too nervous to get picked up and, for him, sex needed leather and rope. Very few leathermen cruise the boulevard. At 18 he finally got into an adult bookstore and found the leather magazines. It took him a while to actually buy one and he read them and tossed them, rather than being caught with one. Most of his life was centered on the beach, the pool, hanging out with friends, drinking beer, having sex with the girls, but there was a craving to be tied up, in leather and be used and controlled. After he had come to college, he was rarely able to jerk off, tie himself up or get away to the city to find a magazine. He got away a couple weeks ago, and found an article which mentioned the club. A week ago Friday, feigning being sick, he left a party where everyone was, went back to his apartment, dressed in his leathers, and found the club. He showed his fake ID and begged to get in. He freaked when he saw me and rushed out. I was doing something to a man strung up, nude, with a hood on. Once he got home, he jerked off imagining himself as being that man. Then it seemed logical to try approaching me in an effort to get out of his class dilemma and, maybe a chance to experience his real sexual interest.
I told him that he was finally being honest with me and with himself. I was going to untie him and then we were going to discuss his performance in my class. Did he now think I would accept his offer?
I let him up, took off the clamps and cock and ball restrictions. He stripped off his drenched leathers. I told him to take a shower. While doing that, I cleaned off his leathers and got us more lemonade.
He came out of the bathroom drying himself off. I told him to stop as I looked at him. “You are truly beautiful.” I told him. He blushed with pleasure.
“Sit down and drink, you are probably dehydrated,” I told him. I love the freedom of young people these days, where they can sprawl about nude.
We began a conversation about school. He didn’t have any real ambitions except to surf and play polo. College was just a way to accomplish this desire. He was passing his two other classes because they were large lecture classes. He had scraped by on the midterms by cramming the night before. I told him that he was bright and capable perhaps to his detriment. It was obvious that he was disciplined. He couldn’t have become that good of a polo player or surfer without work and practice. The same effort applied to academics would make him an honor student.
“But, it is boring. It doesn’t matter to me. I don’t care about that stuff.”
“Yes, Mr. Tucker, that is abundantly apparent. But I have a solution to that. I will not change your grade. You will be ineligible to play. However, in two weeks I can file an additional report. If your work is in the process of being made up, and acceptable, you would no longer be failing my class. I realize that you find my course irrelevant, so I will personally tutor you to help with your motivation.”
I gave him some shorts and sandals and sent him home. I kept his leathers to dry out. He was coming back on Sunday for his tutorial after his morning surfing.


The goals for my course are to teach students to read critically and to write coherently. I give no exams, but each weekend I assign a reading assignment, and on Monday assign an essay on the reading. On Fridays, a quiz consists of a short story and written essay while in the classroom. I told Dave Tucker that he would have to attend all classes and keep current with his work. In addition he would have to write make up essays from reading that I assigned him. He was to do that work at my house under my supervision. I promised him that he would be amply motivated aside from the tape recording. I said these things to him when he arrived on his motorcycle Sunday. I had a plate of sandwiches and a glass of lemonade for him. I also had a chain collar, which I padlocked on his neck. I had him strip and put cuffs on his wrists and ankles. Then I gave him the weekend reading assignment. He sat in the chair and quickly read the assignment. He was bright after all. I worked at my desk. I asked him a few questions to see if he understood the assigned reading. It was clear that he had. I pointed out to him that it would have taken very little time or effort on his part to have avoided his failing grade. He laughed with a seductive look on his face and said, “But then look what I would have missed.”
I had to laugh also, and replied, “Yes, you do have a point there.”
I told him it was time to start to work on his make up assignments. He owed me 8 essays on assigned reading. His smile vanished, replaced with a look of mixed annoyance and resignation.
“If you recall, Mr. Tucker, I did promise to provide a solution to your motivation problem. Here put these on.” I said as I tossed him a pair of leather chastity shorts. “You will need these. But first, since you are so interested in having my cock up your ass, maybe this will suffice for the time being. Ever had one of these before?”
I held up a butt plug. His eyes got wide but his cock grew immediately.
“No, Sir. Does it hurt?”
“This isn’t too big, you need to relax and use plenty of lube, Take it and bend over. Go ahead, be slow and take your time, but get it up there”
As he slowly put it in, he gasped. His cock had gotten so big from that experience, getting his cock through the cock ring of the chastity pants was a challenge. I fastened down his balls, and snapped his cock straight up. I zipped up the padded crotch and locked it in place.
“Your first assignment is to read this story.” I gave him a multi page story from one of my favorite leather magazines. It was an exciting story, but poorly written as the genre usually is. As he read, I could have run a marching band through the room and he wouldn’t have noticed. His right hand was absently rubbing his crotch. It was a good thing that he had those pants on.
When he had finished I had him follow me into my study. In the center of the room I had placed a steel bondage chair with a high narrow ladder-back. I had him sit in the chair and pulled his ankles up and padlocked them to the hooks at the junction of the back chair leg and the seat. Now most all his weight was focused on the unfamiliar butt plug in his ass. Using cotton rope, I crossed his chest and bound his chest and waist to the chair back. The ropes accentuated his gorgeous muscled definition. I placed a hood on his head and buckled on its ball gag. Using the “D” rings on the hood and some cord, I tied the hood to the chair back. Now he could only look straight ahead. Using 2 short chains, I chained his wrist cuff to the ring in the hood’s collar. He could no longer lower his hands below his waist.
I tweaked and fondled his tits, ran my hands over his muscled arms. Then I set a laptop on my drafting table and brought it over to the chair. His eyes could just see the monitor and his hands reach the keyboard.
“I want you to write an essay on the story you just read. Specifically I want you to discuss the writing style and how it helps and impedes the story line. I recognize that you have attended an inadequate number of classes to know much about literary devices and criticism, but I’m seeking your intuition.”
As he began, I stripped off my clothes, and put on my cockring. I fondled my cock as I watched him write. He was aware of my presence beside him but his eyes were forced to stay on the screen.
“Are you finished?”
A grunt which sounded like a “yes”
“Are you in pain?”
A grunt sounding like “no”
Cramping? Nauseated? Need to use the bathroom? Thirsty?
Each reply sounded like a “no”.
“Do you want to be released?”
A grunt sounded like he said “Yes”
I put my hand on his cock padded as it was by the pants.
“Too bad,” I said. “I’m going to grade your essay and you are going to revise it before you are done.” I felt a surge in his cock as I spoke. His fully erect cock told me he was glad that I was in complete control of his body.
I sat on his lap. I looked straight into his eyes. I grabbed his tits and began working them over. He gasped through the gag. He strained and bucked but he kept his eyes fixed on mine. It was a very good sign.
I placed tit clamps on his sensitized tits. Another gasp. Then I buckled the blindfold onto his hood. I watched him for a while. He squirmed as far as his bondage would allow. A small stream of saliva trickled down his chest. His arms and thighs had a sheen of sweat. He was truly beautiful.
I worked on his paper. He did have a good intuitive sense of literary evaluation. I made comments in bold Italics where appropriate on his paper. When I was finished. I got myself a drink, returned, set the keyboard back on the drafting table, and took off his blindfold.
I set him to work again revising his paper, eliminating my italicized comments. When he was finished, he had actually completed a quality paper. I removed his tit clamps to a muffled yell. I dressed and stood behind him, removing his hood, and massaging his straining shoulder and back muscles.
He tried to look to me. “Thank you, thank you.” he murmured.
“It was my great pleasure,” I replied. I began to untie him. He groaned with relief as he was released.
He was more than ready for me to do anything I wanted with him. If I had said the word, he would have bent over and eagerly directed my cock up his virgin ass. If I had wanted him to lick my boots, he would have felt weird but would have done so.
But, alas, he was a student of mine, so I put my arm around his shoulder, praised him for the quality of his work, gave him something to drink, unlocked the chastity pants, and led him to the shower and told him how to take the butt plug out.
“Um, Sir, Do you suppose, I mean, Well, Um, Could we do this again?”
I laughed, my arm affectionately on his shoulder, “For a man who writes concisely, you certainly stumble with the spoken word. Of course we ‘could’ repeat this tutorial method, but I believe you meant to ask if we ‘would.’ Now get in the shower.”
I sent him home. Later that day, I noticed in my shower a glob of creamy yellowish mucous material up near the top of the shower door. He must have had quite an orgasm.


On Monday, I was not surprised to see Dave Tucker in my class. Nor was I surprised to see his countenance display feelings of adoration, seduction, frustration, annoyance, hopefulness, puzzlement, and anger as I treated him no differently than any other student in my course.
So, after polo practice that afternoon, I beckoned him over. He approached with one of those well-honed looks of indifference. “Mr. Tucker,” I began, “You are a student in one of my classes. You and I must be sensitive and respect the appropriate relationship between student and professor. It would be an abuse of power to have any other sort of relationship in the classroom, so long as you are a student of mine. Besides it would be unfair to the other students. Is that clear?”
He appeared crestfallen and sad. It was really quite touching in this big jock.
“Yes, Sir.” He replied
“But,” I continued, “It is quite apparent that the tutorial method we established yesterday is a highly effective tool to stimulate exceptional work. So I will expect you again this Sunday afternoon.”
He smiled and stood up straighter. “Thank you, Sir, What time should I be there?”
“One o’clock will give you time to catch the best morning waves. Study this before you come.” I said as I handed him a card. It was a list of literary devices and techniques with a brief definition and example.
As he left for the shower, I chuckled to see him make that clenched fist exclamation a triumphant “yes.”
On the surface, the rest of the week was no different than any other. Well, except that Dave Tucker attended all his 8AM classes. He, with good nature accepted his classmates teasing and performed well on his assignment. I must admit that I was far too ebullient for a cool leather biker dude personna.