A survey of 65 customers was taken at a bookstore regarding the types of books purchased. The survey found that 41 customers purchased mysteries​, 33 purchased science fiction​, 25 purchased romance novels​, 19 purchased mysteries and science fiction​, 15 purchased mysteries and romance novels​, 10 purchased science fiction and romance novels​, and 5 purchased all three types of books.

​a) How many of the customers surveyed purchased only mysteries​?
​b) How many purchased mysteries and science fiction​, but not romance novels​?
​c) How many purchased mysteries or science fiction​?
​d) How many purchased mysteries or science fiction​, but not romance novels​?
​e) How many purchased exactly two types of​ books?