A reflecting telescope (Fig. 25-21b) has a radius of curvature of 3.0 m for its object mirror

Question:

A reflecting telescope (Fig. 25-21b) has a radius of curvature of 3.0 m for its object mirror and a radius of curvature of -1.50 m for its eyepiece mirror. If the distance between the two mirrors is 0.90 m, how far in front of the eyepiece should you place the photographic film to record the image of a star?