F(A,B,C,D) = ∑ m(0,1,2,3,4,6,8,9,11,12,14)

Step:1

Simplification using K-map

$So, $

$f(A, B, C, D) = (B+D)+(\overline{B} + \overline{D})$

This is the required expression in POS form.

Step:2

Implementation using NOR gates

Taking double inversion of R.H.S.

$ f(A, B, C, D) = \overline{\overline{(B+D)(\overline{B} + \overline{D})}}$

$\hspace{2.5cm}= \overline{\overline{(B+D)}.\overline{(\overline{B}+\overline{D})}}$

Above is the implementation using NOR gate.