5. Let A = P(R). Define f: RA by the formula f(x) = {y < R|y < x}. (a) Find f(2). (b) Is f injective, surjective, both (bijective), or neither? 6. Consider the function f : Z Z given by f(n) = [n+1, if n is even n-3, if n is odd (a) Is f injective? Prove your answer. (b) Is f surjective? Prove your answer.