"i am sorry,madam,but i shall have to charge you twenty dollars for pulling your boy is tooth."''twenty d ollars!why,iunderstand you to say that you charged only four dollars for such work!'' ''yes,but this youngster yelled so terrybly that he scared four otherpatients out ofthe office.'' ''對不起,夫人,為您孩子拔牙我要收取20美元.''''20美元!為什么?不是說好只要4美元. ''''是的,但是您的孩子大喊大叫,把另外4個病人嚇跑了.