Let G be a pseudorandom generator with expansion factor l(n) > 2n. In each of the following cases, say whether G is necessarily a pseudorandom generator. If yes, give a proof; if not, show a counterexample.

(a) Define G(s) = G(s1, , s[n/2]), where s=s1, , sn.

(b) Define G(s) = G((0^|s|) ||s).