A mall has three department stores, J C Penney, Macy’s, and Sears. A survey of 1863 people exiting the mall found that 279 made a purchase at J C Penney, 240 made a purchase at Macy’s, 364 made a purchase at Sears, 76 made a purchase at J C Penney and Macy’s, 108 made a purchase at J C Penney and Sears, 95 of them made a purchase at Macy’s and Sears, and 23 of them made a purchase at all three stores.
a) How many people made a purchase at Macy’s but did not make a purchase at Sears?
b) How many people made a purchase at exactly one of the three stores?