At Aberdeen Uni, 4 sophomores were taking Biology. They had done brilliantly in labs, on practicals and tests, with each having an overall 'A' grade so far during the semester.

They were so confident before finals that they decided to head down to Edinburgh College for a big party with some mates. A great time was had by all, to such an extent that they slept all Sunday, and didn't make it back to Aberdeen till early Monday morning.

Rather than take the final then, they decided to find the Professor after the exam and explain their trip, how they had planned to be back in time to study, but unfortunately had a flat tire on the way home, didn't have a spare, couldn't get help and thus missed the final.

The Professor thought it over, agreed they could take the exam the next day, and the guys were lightily relieved. That night they studied hard, arrived the next day, where upon the professor placed them each in separate rooms. Handing them a test booklet he told them to begin.

Looking at problem 1, worth five points, "Cool", they thought at the same time, each in his separate room, "This will be a cinch."

Each finished the problem 1, turned the page and found written:
2) [For 95 points]: Which tire?