Find all the prime implicants for the following Boolean functions, and determine which are essential: (a) F (A, B, C, D) = Σ(0, 2, 3, 5, 7, 8, 10, 11, 14, 15) (b) F (A, B, C, D) = Σ(2, 3, 4, 5, 6, 7, 9, 11, 12, 13) (c) F (A, B, C, D) = Σ(0, 1, 2, 5, 7, 8, 9, 10, 13, 15)