(a) Let : C C be an isomorphism such that, for every a Q, p(a) = a. Let z C be a root of f(X) Q[X]. Prove that (2) is also a root of f(X). (b) Let @ : F[X] F[X] be an isomorphism such that (a) = a for every a F. Prove that f F[X] is irreducible if and only if (f) is irreducible. Give an example of an isomorphism : F[X] F[X] such that (a) = a for every a F but is not the identity