Using the Pumping Lemma, please.

Prove that the following langauges are not regular (a) L = {ww: w {a,b}*} (b) L = {a"yle: n > k} (c) L = {abmck: n + m >k>0} (d) L = {w E {a,b}* : 2na(w) = 3nb(w)}