求助：涛涛数学第5套第28题~求助呀！！

kicobao

Q28:

Last Sunday a certainstore sold copies of Newspaper A for $1.00 each and copies of Newspaper Bfor $1.25 each, and the store sold no other newspapers that day.  If r percent of the store’s revenuesfrom newspaper sales was from Newspaper A and if p percent of thenewspapers that the store sold were copies of newspaper B, which of the following expresses r in terms of p?

A.   100p /(125 – p)

B.    150p /(250 – p)

C.    300p /(375 – p)

D.   400p /(500 – p)

E.    500p /(625 – p)

这题答案给的是D~但是我自己真心算不出来D啊~~
求大家指点指点，看看这题是不是条件有误？还是我算法上有问题？

我是设总量卖出X份报纸，所以卖出的B类报纸有XP/100份，而A类报纸就有(1-P/100)X份
所以r=[(1-p/100)X]/[(1-P/100)X+(XP/1OO)1.25]
这样算出来再怎么也不能是D啊~
算出来r=（400-4P)/(400+P)

求助啊~~~阿弥陀佛~~~