A programmer and an engineer were sitting next to each other on an airplane. The programmer leans over to the engineer and asks if he wants to play a fun game. The engineer just wants to sleep so he politely declines, turns away, and tries to sleep. The programmer persists and explains that it's a real easy game. He explains, "I'll ask a question and if you don't know the answer you pay me $5. Then you ask me a question and if I don't know the answer I'll pay you $5." Again, the engineer politely declines and tries to sleep.
The programmer, now somewhat agitated, says, "OK, if you don't know the answer, you pay me $5, and if I don't know the answer, I'll pay you $50!" Now, that got the engineer's attention, so he agrees to the game. The programmer asks the first question, "what is the distance from the earth to the moon?" The engineer doesn't say a word and just hands the programmer $5.
Now, it's the engineer's turn. He asks the programmer, "what goes up a hill with three legs and comes down on four?" The programmer looks at him with a puzzled look, takes out his laptop computer, looks through all his references and after about an hour wakes the engineer and hands him $50. The engineer politely takes the $50, turns away, and tries to return to sleep.
The programmer, a little miffed, asks, "Well? What's the answer to the question?" Without a word, the engineer reaches into his wallet, hands $5 to the programmer and returns to sleep.