Solution
= Solution
\b[No.] Every estimator in parts (b) and (c) has $a\ne1$, so its risk contains the nonconstant quadratic term
$((a-1)\theta+b)^2$ and has infinite supremum over $\theta\in\mathbb R$. The estimator $\overline X_n$ has constant risk $1/n$, so those estimators cannot be <minimax estimator>[minimax].