周末放学回家,明明看见桌子上有一张电费收据,他拿起来仔细一看,收据上电费的单价有两种,一种是峰时电价,一种是谷时电价。他有些不明白,自己家的用电怎么还分两种呢?难道收据打错了?这时,妈妈推门进来,明明指着电费收据问妈妈:“咱家这个月的电费怎么还两种价格呀?什么是峰时?什么是谷时?是不是打错了?” Weekend home after school, obviously saw the table with a receipt of electricity, he took a closer look, the receipt of the electricity price of two, one is the peak hour price, one is the valley when the price. Some of his do not understand how his home is divided into two kinds of electricity it? Is the receipt wrong? At this time, the mother pushed the door came in, obviously pointing to the electricity receipt to ask her mother: “ What is the peak? What is the valley? Is not wrong? ”