Answer
$f=\infty$, $r=\infty$
Work Step by Step
The lens equation states that $$\frac{1}{f}=\frac{1}{d_o}+\frac{1}{d_i}$$ In a mirror, the object distance and image distance are the same. Therefore, $$\frac{1}{f}=\frac{1}{d_o}-\frac{1}{d_o}=0$$ This means that $$\frac{1}{f}=0$$ Therefore, the focal length must be infinitely large. Since $f=\frac{R}{2}$ and $f=\infty$, $R$ must also be infinitely large.