"Daddy, can I learn to play the violin?" young Sarah asked her father. She was always asking for things, and her father was not pleased.
"You cost me a lot of money, Sarah," he said. "First you wanted to learn horse riding, then dancing, then swimming. Now it's the violin."
"I'll play every day, Daddy," Sarah said. "I'll try very hard."
"All right," her father said. "This is what I'll do. I'll pay for six weeks of lessons. At the end, you must play something for me. If you play well, you can have more lessons. If you play badly, I will stop them."
"OK, Daddy," Sarah said. "That is fair."
He soon found a good but expensive violin teacher, and Sarah began her lessons. Her father kept his promise.
The six weeks passed quickly. It was time for Sarah to play for her father.
She went to the living room and said, "I'm ready to play for you, Daddy."
"Fine, Sarah," her father said. "Begin."
She began to play. She played very badly, making a terrible noise. Her father had a friend with him, who put his hands over his ears.
When Sarah finished, her father said, "Well done, Sarah. You can have more lessons." Sarah ran happily out of the room.
Her father's friend turned to him. "You've spent a lot of money, but she still plays very badly," he said.
"Well, that's true," her father replied. "But since she started learning the violin, I've been able to buy five apartments in this building very cheaply. In another six weeks, I'll own the whole building!"