A computer programmer and an engineer were sitting next to each other on a transcontinental flight.

The programmer leaned over to the engineer and asked whether he would like to play a game. 

The engineer only wanted to take a nap, so he politely declined, rolled over toward the window and closed his eyes.

The programmer persisted and stated that the game was both very easy and a lot of fun. 

He explained "I ask you a question - if you don't know the answer, you pay me five bucks. 

Then you ask me a question, and if I don't know the answer, I'll pay five bucks to you."

Again, the Engineer politely declined and closed his eyes. 

The programmer, somewhat agitated, said, "OK, if you don't know the answer you pay me five bucks, but if I don't know the answer, I'll pay you fifty bucks!"

This caught the engineer's attention, and-seeing no end to his torment unless he played the game-agreed to play.

 The programmer asked the first question: "What's the distance between the Earth and the Moon?"

The engineer wordlessly reached into his wallet, pulled out a five dollar bill and handed it to the programmer.

Now it was the engineer's turn. 

He asked the programmer: "What goes up a hill with three legs, and comes down on four?" 

The programmer looked puzzled, then took out his laptop computer and searched through all his reference material.

 He tapped into the AirPhonex with his modem and searched through the Internet and the Library of Congress, all to no avail. 

Then he sent urgent E-mail inquiries to all of his brightest colleagues, but could find no help anywhere.

After an hour or so he woke the engineer and forked over $50. 

The engineer accepted the money politely and closed his eyes again.

The programmer, more than slightly frustrated, shook the engineer's shoulder and demanded,

 "So, what's the answer?"

The engineer just smiled, reached again into his wallet, handed the programmer a five dollar bill, and went right
back to sleep.