riddle

A dumb lady is on an airplane just about to go to sleep, when a man sits next to her and says let's play a game. She agrees and he explains the game. He says, "I will ask you a question, and if you can't answer you give me 5.00, then you ask me a question, and if I can't answer I will give you 50.00". So the man asked his first question. "What is the highest mountain?" Not knowing the answer, she gives him 5.00. Then she asks her question "What goes up a mountain with four legs, and comes down with five?" Not knowing he gives her 50.00. He then asked her what the answer was. Secretly she gave him 5.00 dollars.