6. Assume that b > 0, b / 1. (a) Prove that if a > 0, then the derivative of f(x) = log, x at x = a is alng, where In b = log, b. (b) Prove that for any a E R, the derivative of g(x) = b at x = a is (In b)b". In particular, notice that the derivative of e" at x = a is e"