The Expensive Tooth

One day,a mother took his son to pull his tooth.

And after the worker,the doctor said to the mother,"It is OK now,madam.And the price is twenty-five dollars."

"What?Twenty-five dollars?"Shouted by the mother."That is expensive,I know you have charged five dollars for an extraction."

"Well,come calm."Smiled by the doctor."I usually do,but Mrs,your son shouted so loudly that I lost four patients.So...."