A Point source of light B is placed at a distance L in front of centre of a mirror of width d hung vertically on a wall. A man walks in front of the mirror along a line parallel to mirror at a distance 2L from it as shown. Find greatest distance over which he can see the image of light source in mirror.

Question

$(a)\;d \\ (b)\;3d \\ (c)\;2d \\ (d)\;4d$