n! n! For the given values of n and r, evaluate (a) r!(n - r)! for n = 13 and r = 6. (n - r)! and (b) n! (a) When n = 13 and r = 6 (n- r)! (Simplify your answer. Type an integer or a simplified fraction.) n! (b) When n = 13 and r= 6, r! (n- r)! (Simplify your answer. Type an integer or a simplified fraction.)