A survey of 60 customers was taken at a SF bookstore regarding the types of books purchased

A survey of 60 customers was taken at a SF bookstore regarding the types of books purchased. The survey found that 36 customers purchased mysteries, 28 purchased science fiction, 19 purchased romance novels, 14 purchased mysteries and science fiction, 10 purchased mysteries and romance novels, 7 purchased science fiction and romance novels, and 3 purchased all three types of books. To figure out how many purchased exactly two types of books Chris made this Venn diagram showing ing cardinality of each region. So, how many purchased exactly two types?