W'X' W'X  WX  WX' 

 Y'Z'    X    1   1      

 YZ'     X        1   1 

 YZ      X    1       1

 YZ'     X            

 g1 = x'z + w'yz + w'y'z' + wxy'

 g2 = x'z + w'yz + xy'z' + wxy'

 g3 = x'z + w'yz + xy'z' + wy'z