Optimize the following Boolean functions $F$ together with the don't$-$care conditions $d$ :

$($a$)F(A,B,C)=m(2,4,7),d(A,B,C)=m(0,1,5,6)$

$($b$)F(A,B,C,D)=m(2,5,6,13,15),d(A,B,C,D)=m(0,4,8,10,11)$

$($c$)F(W,x,Y,Z)=m(1,2,4,10,13),d(W,x,Y,Z)=m(5,7,11,14)$