Asurvey of 120 college junior business students produced these results: 40 read a national newspaper, 48 read the local paper,70 read the campus paper, 25 read a national newspaper and the local paper, 28 read the local paper and the campus paper, 21 read the campus paper and the national paper, and 18 read all three.

a. how many do not read any of the papers?
b. how many read a national paper and the local paper but not the campus paper