Joke: Good Work-Fool joke

Weary of constantly picking clothes up from the floor of her son's room, a mother finally laid down the law: each item of clothing she had to pick up would cost her son 25 cents. 

By the end of the week, he owed her $1.50. She received the money promptly, along with a 50 cent tip and a note that read, "Thanks, Mom; keep up the good work!"