Cryptography

If f is a binary relation between sets A and B with |A| ordered pairs in the relation and every element of A occurs exactly once as a first element in an ordered pair, then the relation can be viewed as a function f: A --> B

a) Let A = {1,2,3) and B = {a,b,c). Is f = {(1,a), (2, b)) an invertible function? inverse (given as a stt of ordered pairs). If not, explain in one short sentence. If so, what is its b) Let A- (1,2,3 and B a,b,c. Is f (1,a), (2,b), (3,b)) an invertible function? If so, what is its inverse (given as a set of ordered pairs). If not, explain in one short sentence. c) Let A = {1,2,3) and B = {a,b,c). Is f = {(1, a), (2, b), (3c)) an invertible function? If so, what is its inverse (given as a set of ordered pairs). If not, explain in one short sentence