Two plane mirrors meet at a right angle along a vertical edge. A small light source is positioned 12cm from each mirror on the line that bisects the 90∘ angle between them. Consider the image that results from two successive reflections—first in one mirror, then in the other. What is the straight-line distance between this double-reflected image and the original light source?
a) 24cm
b) 242cm
c) 48cm
d) 122cm