A point source of light $S$, placed at a distance $60 \mathrm{cm}$ infront of the centre of a plane mirror of width $50 \mathrm{cm}$, hangs vertically on a wall. A man walks infront of the mirror along a line parallel to the mirror at a distance $1.2 \mathrm{m}$ from it (see in the figure). The distance between the extreme points where he can see the image of the light source in the mirror is__$\mathrm{cm}$