$f(a,b,c,d) = \sum{(0,2,5,7,8,10,13,15)}$ Sum of Minterms(SOP)
$f(a,b,c,d) = \Pi{(0,2,5,7,8,10,13,15)}$ Product of Maxterms(POS)
Using $k-$map,we get
$f(a,b,c,d) = B'D'+BD$ (SOP)
$f(a,b,c,d) = (B'+D)\cdot(B+D')$ (POS)
Using the POS,we can easily make NOR gate.