GMATPrep上的题目请教

17 DS

If N and M are positive integers,what is the remainder when 3^(4N+2) is divided by 10?

(1)            N=2

(2)            M=1

我选的是A，而答案是B。当时在做的过程中，我就很奇怪，M在整题中都没出现过，为什么在条件中还有M=1。后来发现答案选B，难道说是3^(4M+2)，可是我觉得那字母怎么看都像N，而非M啊，难道说在考试界面中，M和 N是难以辨别的？

25 Rates for having a manuscript typed at a certain typing service are $5 per page for the first a page is typed and $3per page each time a page is revised.If a certain manuscript has 100pages,of which 40 were revised only one,10 were revised twice,and the rest required no revisions,what was the cost of having the manuscript typed?

(A)$430

(B)$620

(C)$650

(D)$680

(E)$720

key,题目看的有点迷糊

25.100pages的manuscript,

先被type一次,5*100=500$,

然后40pages被revise一次,40*3=120$,

      10pages被revise两次,10*3*2=60$,

最后500+120+60=680

17题我也没看懂