Three men with degrees in mathmatics, physics and biology are locked
up in dark rooms for research reasons.

A week later the researchers open the a door, the biologist steps out
and reports: `Well, I sat around until I started to get bored, then
I searched the room and found a tin which I smashed on the floor.
There was food in it which I ate when I got hungry. That's it.'

Then they free the man with the degree in physics and he says:
`I walked along the walls to get an image of the room's geometry, then
I searched it. There was a metal cylinder at five feet into the room
and two feet left of the door. It felt like a tin and I threw it at
the left wall at the right angle and velocity for it to crack open.'

Finally, the researchers open the third door and hear a faint voice
out of the darkness: `Let C be an open can.'