Keep the change

Mr. Chang was very angry at Tonny because he said dirty words in class. Therefore he decided to teach him a lesson.

"Tonny. As I metioned earlier, those who say dirty words in class will have to pay five dollars to us as a fund for the class. Pay us now!"

"Okay, Mr.Chang. Here is ten dollars. Would you make change for me?" Tonny said to him.

"Sure. Let me check if I have some in my pocket...Ooops! I am afraid that I don't....", Mr. Change was embarrased a bit.

"Fuck!!" Tonny shouted at Mr. Chang in front of the class and went, "Keep the change. Mr. Chang."