An object is placed at a distance `2f` from a concave mirrorr of focal length `f`. Light reflected from the mirrorr falls on a plane mirrorr. The distance of the plane mirrorr from the concave mirrorr equals `f`. The distance of the final image (due to reflection at both concave and plane mirror) from the concave mirrorr is
A. `f`
B. `f//2`
C. `2f`
D. zero