f(a,b,c,d) = summation of minterms(0,1,4,5,10,11,14)

 The function f'(a,b,c,d) = summation of minterms(2,3,6,7,8,9,12,13,15)

        a'b' a'b  ab   ab' 

 c'd'    1    1    

 cd'     1    1 

 cd                     1

 cd'             1      1

 The one minimum solution for f and the two equally good solution ofr sum of products for f' are

  f = a'c' + ab'c + acd'

 f' = ac' + a'c + abd

  f' = ac' + a'c + bcd