the lawyer & the blonde

A lawyer and a blonde woman are seated next to each other on a long flight. The lawyer asks if the woman would like to play a game. The blonde is tired and just wants to take a nap, so she politely declines, and tries to catch a few winks.
The lawyer persists, saying the game is a lot of fun: "I ask you a question, and if you don’t know the answer, you pay me only $5; you then ask me a question, and if I don’t know the answer, I pay you $500!"
This catches the blonde’s attention, and to keep him quiet, she agrees to play. The lawyer asks the first question, "What’s the distance from the earth to the moon?"
The blonde doesn’t say a word, reaches into her purse, pulls out a $5 bill and hands it to the lawyer.
Now it’s the blonde’s turn. She asks the lawyer, "What goes up a hill with three legs and comes down with four?"
The lawyer uses his laptop, searches the Net, makes Airphone calls. He even SMS all his smart friends, all to no avail. After a futile hour of searching, he gives up. Meekly, he wakes up the blonde and hands her $500. The blonde takes the $500 and goes back to sleep.
The lawyer is driven mad not knowing the answer. He wakes her up again and asks, "Well, so what goes up a hill with three legs and comes down with four?"
The blonde reaches into her purse, hands the lawyer $5, and goes back to sleep.