At what angle should a ray of light be incident on the face of a prism of refracting angle $60^{circ}$ , So that it just suffers total internal reflection at the other face ? The refractive index of the prism is $1.524$

Question

$\begin{array}{1 1} 25^{\circ}45' \\ 19^{\circ}45' \\ 29^{\circ}45' \\ 20^{\circ}45' \end{array}$