A light ray is incident, at an incident angle $\theta_1$, on the system of two plane mirrors $\mathrm{M}_1$ and $\mathrm{M}_2$ having an inclination angle 75° between them (as shown in figure). After reflecting from mirror $\mathrm{M}_1$ it gets reflected back by the mirror $\mathrm{M}_2$ with an angle of reflection 30°. The total deviation of the ray will be .............. degree.