PREP2-DS-210，为何答案是E？？

210.
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For each order, a mail-order bookseller charges a fixed processing fee and an additional shipping fee for each book in the order.  Rajeev placed five different orders with this bookseller--an order for 1 book in January, an order for 2 books in February, an order for 3 books in March, an order for 4 books in April, and an order for 5 books in May.  What was the total of Rajeev's processing and shipping fees for these five orders?

(1)  Rajeev's processing and shipping fees were $1.00 more for his order in March than for his order in January.

(2)  The total of Rajeev's shipping fees for the five orders was $7.50.

其实如果processing fee和shipping fee都是固定的话，我把前者设为X，后者设Y。那么：

1. 由条件1可以算出X+Y=0.5，那么就可以求出5次orders的总processing and shipping fees啦

2. 由条件2客户得到Y=0.5,单独不能得到答案

那么按照我的思路，答案应该是A。但是官方答案是E，为什么？我那里想错了？请各位考友帮忙，谢谢！

PS：我是3月31日上战场（广州），有为GG发email给我说31号是裸考，但是我也没办法，因为广州考场只有4个考位，3月份位置都是满的，想改都不行。唯有坦然应战了~~~

由条件1可以算出X+Y=0.5 为啥啊这是？

条件一， 得出2y=1.0

条件二， 得出15y=7.5

求不出x啊

MM请看清楚条件1：Rajeev's processing and shipping fees were $1.00 more for his order in March than for his order in January

这里可以写出公式：X*3+Y*3=(X+Y)+1 => X+Y=0.5 (NOTE:processing and shipping fees 是X+Y)

charges a fixed processing fee and an additional shipping fee for each book in the order

难道不是 (x+3y)-(x+y)

a fixed processing fee and an additional shipping fee for each book in the order

如果题目是a fixed processing fee in each order的话，那你的说法就有道理。但是，我不确定题目的意思是不是能理解为a fixed processing fee and an additional shipping fee for each book in the order,如果是这样的话，那就应该按照我的方法算了。是不是题目意思有歧义啊？？

不过OA是E，所以可能题目意思是 a fixed processing fee in each order 了，谢谢！