R U Psychic?

A Supposed True Finals Story

This past fall semester, at Duke University, there were two sophomores
who were taking Organic Chemistry and who 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'. These two friends were so confident going
into the final that the weekend before finals week, even though the
Chem final was on Monday, they decided to go up to University of
Virginia and party with some friends up there. So they did this and
had a great time. However, with their hangovers and everything, they
overslept 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
Aldric 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, but that they had a flat tire
on the way back and didn't have a spare and couldn't get help for a
long time and so were late getting back to campus.

Aldric 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
Aldric 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
free radical formation 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?