Little Johnny walked into the kitchen, saw his mother making a
cake and announced, "I'll be playing in my room for the next two hours.
I sure would like a piece of cake when you're finished."
Later, when his mother brought him a piece of cooled cake, Little Johnny
exclaimed, "Gee, it worked!"
Puzzled, his mother asked, "What do you mean?"
Little Johnny replied, "Daddy said that in order to get a piece around here, you
have to spend a couple of hours playing first!"