(a)[1]
Shade the part of the Venn diagram that corresponds to $(A \cap B)' \cup (B \cap C)'$.
(b)[2]
On one morning, $50$ people go to a library. Of these, $35$ borrow a book. Also, $12$ use a computer. A total of $8$ neither borrow a book nor use a computer. Using a Venn diagram, or by any other method, determine how many people use a computer but do not borrow a book.