$3\mathrm{.}8$ Derive a minimum sum$-$of$-$products $($SOP$)$ form for each of the following incompletely specified functions using a Karnaugh map.

a$.G_1(A,B)={\displaystyle \underset{?}{\overset{?}{}}}m(0,2)+{\displaystyle \underset{?}{\overset{?}{}}}d(3)$

b$.G_2(A,B,C)=$prodM$(0,3)*D(1,2,5)$

c$.G_3(A,B,C,D)={\displaystyle \underset{?}{\overset{?}{}}}m(1,3,7,8,10,12)+{\displaystyle \underset{?}{\overset{?}{}}}d(0,2,4,9,11,13,14)$