This is College Physics Answers with Shaun Dychko. The magnification of this telescope will be the negative of the focal length of its objective mirror divided by the focal length of the eyepiece. So, the focal length for a mirror is half of its radius of curvature. So, we'll substitute <i>R</i> over two in place of <i>Fo</i>. So, magnification is negative <i>R</i> over two times one over the focal length of the eyepiece. So, that's negative ten meters divided by two times three meters, which is negative 1.67 magnification.