A graduate student of mathematics who used to come to the University on foot every day arrives one day on a fancy new bicycle. "Where did you get the bike from?" his friends asked. "It's a `thank you' present", he explains, "from that freshman girl I've been tutoring. Yesterday she called me and told that she had passed her math final and wanted to drop by to thank me in person. She arrived at my place on her bicycle. When I had let her in, she took all her clothes off, smiled at me, and said: `You can get from me whatever you desire!'" One of his friends remarks: "You made a really smart choice when you took the bicycle." "Yeah", another friend adds, "just imagine how silly you would have looked in a girl's clothes - and they wouldn't have fit you anyway!"