A short rod of length l and negligible diameter lies along the optical axis of a concave minor at a distance of 3 m. the focal length of the mirror is 1 m and l

A short rod of length L and negligible diameter lies along the optical axis of a concave minor at a distance of 3 m. The focal length of the mirror is 1 m and L << 1 m. If L' is the length of image of the object in the mirror, then (A) =4 (B) (C) L (D) 16