A lawyer and a young lady were sitting next to each other on a long flight. The lawyer asked if she would like to play a fun game. The lady just wanted to take a nap, so she politely refused. The lawyer explained that the game was actually very easy. He explained "I ask you a question, and if you don't know the answer, you pay me, and vice versa ." Again, the lady politely refused and tried to get some sleep. The lawyer added eagerly, "Okay, if you don't know the answer, you pay me $5, and if I don't know the answer, I will pay you $50!" Considering that there would be no end to this suffering unless she played, the lady agreed. The lawyer asked the first question, "What is the distance from the earth to the moon?" The young lady didn't say a word, pulled out five dollars from her purse and handed it to the lawyer. Now, it was the lady's turn. She asked the lawyer, "What goes up a hill with three legs, and comes down with four?" The lawyer was greatly puzzled. He took out his computer and searched all of his references. He searched the Net and sent e-mails to all of his friends, but it was all _ . After over an hour, he woke up the lady and handed her $50. The lady politely took the money and turned away to get back to sleep. The lawyer, very puzzled now, woke the lady up again and asked, "Well, what on earth is the answer?" Without a word, the lady reached into her purse, handed the lawyer another $5 and went back to sleep. The author's purpose for writing the story is to  _  .
tell us how clever the lady is describe the rules of playing games show that it is interesting to play games make fun of the lawyer