W'X' W'X  WX  WX' 

 Y'Z'   1     1    1   1 

 YZ'          1     

 YZ           1    1   1

 YZ'   

  From the map, high outputs are for 0,1,2,3,5,13,14,15 

   0.   0.   0.   0.
   0.   0.   0.   1.
   0.   0.   1.   0.
   0.   0.   1.   1.
   0.   1.   0.   1.
   1.   1.   0.   1.
   1.   1.   1.   0.
   1.   1.   1.   1.

  Evaluating expression from truth table and map 

!W'X'Y' Z'  +  W'X'Y'Z  +  W'X'Y Z'  +  W'X'YZ  +  W'XY'Z  +  WXY'Z  +  WXY Z'  +  WXYZ  !

 Three different reduced expression using boolean algebra

 F = Y'Z' + WYZ + W'XZ'