A 1 (a) Let A, B, C, D be sets with IA | = | C I and IB I = I D I. Then applies

IA x BI = /C x D/?

If so, prove the statement. If not, give a counterexample

to.

(b) Let X = {x1,x2, x3} be a three-element set. How many injectives, surjek-

are there active and bijective images from X to X?