Knock knock....poo.....just kidding

Introductory Chemistry at Duke has been taught by wise old Professor Bonk for many years. One year there were these two guys who were taking Bonk's Chemistry class. They both did pretty well on all of the quizzes and the midterms and labs, etc., such that going into the final they had a solid A. They were so confident going into the final, that the weekend before finals week they decided to go up to UVirginia and party with some friends. So they did this and had a great time. However, with their hangovers and everything, they slept all day Sunday and didn't make it back to Duke until early monday morning. Rather than taking the final then, what they did was to find Professor Bonk after the final and explain to him why they missed the final. They told him that they went up to UVa for the weekend, and had planned to come back in time to study. Unfortunately they had a flat tire on the way back. Since they didn't have a spare, and couldn't get help for a long time, they were late getting back to campus. Bonk thought this over and then agreed that they could make up the final on the following day. The two guys were elated and relieved.

So, they studied that night and went in the next day at the time that Bonk had told them. He placed them in separate rooms and handed each of them a test booklet and told them to begin. They looked at the first problem, which was something simple about molarity and solutions and was worth 5 points. "Cool" they thought, "this is going to be easy." They did that problem and then turned the page. They were unprepared, however, for what they saw on the next page. It said:

(95 points) Which tire?