A light ray is incident, at an incident angle \( \theta_1 \), on the system of two plane mirrors \( M_1 \) and \( M_2 \) having an inclination angle \( 75^\circ \) between them (as shown in figure). After reflecting from mirror \( M_1 \) it gets reflected back by the mirror \( M_2 \) with an angle of reflection \( 30^\circ \). The total deviation of the ray will be ________ degree.
