4.2 Of 25 microcomputers available in a supply room, 10 have circuit boards for a printer, 5 have circuit boards for a modem, and 13 have neither type of board. Using P to denote those that have printer boards and M to denote those that have modem boards, symbolically denote the following sets, and give the number of microcomputers in each set.

a Those that have both boards.

b Those that have neither board.

c Those that have printer boards only.

d Those that have exactly one of the boards.