Answer
$f_o \approx4.7m$
$r= 9.3m$
Work Step by Step
Use equation 25-3 to find the magnification of the telescope. The objective is a converging mirror, with positive focal length. The magnification is negative.
$$M=-\frac{f_o}{f_e}$$
$$f_o=-Mf_e=-(-150)(0.031m)=4.65m \approx4.7m$$
The focal length of the mirror (the objective) is half the radius of curvature, f = r/2. Double the focal length to find the radius of curvature.
$$r= 2f = 9.3m$$
