Final output $= \sum 0,1,2,4,5,8$
- $f_1(w,x,y,z) = \sum 0,1,2,3,5,12$
- $f_2(w,x,y,z) = \sum 0,1,2,10,13,14,15$
- $f_3(w,x,y,z) = \sum 2,4,5,8$
$f1\text{ AND }f_2$ will give the common minterms - $f_{12} =\sum 0,1,2.$
Now $f_{12} \text{ OR } f_3 = \sum 0,1,2,4,5,8.$