编写一个电费核算系统：电费计算模型：用户电费收取与电价和用户类别相关，目前电价按不同的划分方式有不同的种类，按照用电类别划分，可分为居民生活电价、非居民生活电价、商业电价、非普工业电价、大工业电价等。

功能要求：

(1)　　参数维护：用户类型及用户电价，存储在文件中；

(2)　　按照实际电费计算模型进行电费正确计算，计算结果存储在文件中，并以表格形式输出；

(3)　　电费查询：查询并显示指定用户指定时间段的电费记录；

(4)　　系统统计功能：按照月、季度、年度分别统计。-Write a tariff accounting systems: tariff calculation model: the user electricity tariffs and user charges categories associated with the current price divided by the different ways there are different types, in accordance with the type of electricity can be divided into living electricity Non-living price, commercial price, non-ordinary industrial tariffs and other large industrial electricity.

Functional requirements:

(1) parameters of maintenance: the user types and user price, stored in a file

(2) the actual electricity tariff calculation model correctly computed and the results stored in the file, and output in tabular form

(3) electricity query: Query and display the specified time period specified by the user of electricity records

(4) system statistical functions: According to the monthly, quarterly and annual statistics, respectively.