(a) A concave spherical mirror forms an inverted image different in size from the object by a factor a > 1. The distance between object and image is d. Find the focal length of the mirror. (Use any variable or symbol stated above as necessary.)
(b) Suppose the mirror is convex, an upright image is formed, and 1>a. Determine the focal length of the mirror. (Use any variable or symbol stated above as necessary.)