Find the minimal sum and distinguished 1-cell using Karnaugh Maps for the following functions, also state essential prime implicants (if any) and which are non-essential prime implicants (if any)
a. F = fA,B,C,D (2, 3,4,6,7,12,13,14,15)
b. F= fA,B,C,D (1, 3,5, 9, 12, 13, 14)