14. Simplify the following functional expressions using Boolean algebra and its identities. List the identity used at each step.

a) F(x, y, z) = y (x′ + (x + y)′)

b) F (x, y, z) = x ′yz + xz

c) F (x, y, z) = (x′ + y + z )′ + xy′z′ + yz + xyz