Let $X$ be a binomial random variable with parameters $n$ and $\Theta$. Suppose that $\Theta$ has a beta distribution with parameters $\alpha$ and $\beta$.
(a) Show that $f_{\Theta}(\theta \mid X=k)$ is a beta pdf with parameters $a+k$ and $\beta+n-k$.
(b) Show that the minimum mean square estimator is then $(\alpha+k) /(\alpha+\beta+n)$.