Revisit (a) if g is a group such that tc s cyclic, where z(g) is centre of g then show that g is zg abelian (b) show that a finite semi-group in which cross can

Revisit (a) If G is a group such that tC s cyclic, where Z(G) is centre of G then show that G is zG abelian (b) Show that a finite semi-group in which cross cancellation holds is an abelan group