一个简单的超市购物系统的编程，定义一个货物Goods类，它派生3种不同的电器子类：冰箱、彩电、空调。

然后各创建一个实际的对象，即顾客购买了3种电器，比如：海尔冰箱、长虹彩电、格力空调。使用虚函数，求这些电器价格之和。

-A simple programming supermarket shopping system, define a class of goods Goods, which derives the electrical sub 3 different categories: refrigerators, color TV, air conditioning. Then create an actual object of all that the customer purchased 3 appliances, such as: Haier refrigerator, color TV Changhong, Gree air-conditioning. Use of virtual functions, and find the price of these appliances.