Let R and S be relations on the set {a, b, c, d, e, f}: R = {(a, b), (b, d), (c, b), (d, e), (d, f)} S = {(b, a), (b, c), (d, b), (d, d), (e, b), (f, d)} Find: a) The reflexive closure of R, b) The symmetric closure of R, c) The transitive closure of R, d) The reflexive closure of S, e) The symmetric closure of S, f) The transitive closure of S. Prove or disprove: If R Ls a partial order on set A, then the symmetric closure of R is an equivalence relation