Jenny was a very naughty girl. One day, while passing through a market, she saw a stationery shop and thought of teasing it's owner.
She went to the shopkeeper and asked for a pen. The shopkeeper took out a pen and asked her to try it. She wrote something on her notebook and then said to the shopkeeper that she didn't like the pen. Then the shopkeeper showed her the second, then the third and then so many other pens. At last he got frustrated and asked Jenny what kind of a pen she wanted.
Jenny said that she didn't need the pen anymore as she had already completed her homework. The shopkeeper had no words to say.