One face of a prism is silvered and if refracting angle $30^{\circ}$ and refracting index 1.414 is silvered . At what angle must a ray of light fall on the silvered surface so that after refraction into prism and reflection at the silvered surface it retrace the path ?

Question

$\begin{array}{1 1} 45^{\circ} \\ 90^{\circ} \\ 60^{\circ} \\ 30^{\circ} \end{array}$