(a) If $f(z)$ is analytic inside and on the simple closed curve $C$ enclosing $z=a$, prove that
$$
\{f(a)\}^n=\frac{1}{2 \pi i} \oint_C \frac{\{f(z)\}^n}{z-a} d z \quad n=0,1,2, \ldots
$$
(b) Use (a) to prove that $|f(a)|^n \leq M^n / 2_\pi D$ where $D$ is the minimum distance from $a$ to the curve $C$ and $M$ is the maximum value of $|f(z)|$ on $C$.
(c) By taking the $n$th root of both sides of the inequality in (b) and letting $n \rightarrow \infty$, prove the maximum modulus theorem.