A prism of refractive index $\mu =1.5$ of vertical angle $6 ^{\circ}$ is placed in front of a mirror. A ray of light is incident normally on one of the face of the prism as shown. What is the total deviation caused by the system.

Question

 

$(a)\;4^{\circ} \\ (b)\;3^{\circ} \\ (c)\;177^{\circ} \\ (d)\;174^{\circ}$