Two Plane Mirrors Make an Angle Of $30 ^ { \circ }$

Multiple Choice

Two plane mirrors make an angle of $30 ^ { \circ }$ with each other. A light ray enters the system and is reflected once off of each mirror. Through what angle is the ray turned?

A) $150 ^ { \circ }$
B) $60 ^ { \circ }$
C) $120 ^ { \circ }$
D) $90 ^ { \circ }$