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?