Answer
$M=-110$
Work Step by Step
The focal length of the mirror (the objective) is half the radius of curvature.
$$f = \frac{r}{2} = \frac{6.1m}{2} = 3.05m\approx 3.1m$$
Use equation 25-3 to find the magnification of the telescope.
$$M=-\frac{f_o}{f_e}=-\frac{0.5(6.1m)}{0.028m}\approx-110$$
