示例文件结构如下
Product,Base_Price,Promotion_Price,Discount
Shampoo,1.999999,1.409999,15.9988999
Biscuit,2.999999,2.409999,15.9988999
输出文件应采用以下格式：
Product,Base_Price,Promotion_Price,Discount
Shampoo,1.99,1.40,15.99
Biscuit,2.99,2.40,15.99