A light ray enters a rectangular glass slab at angle $$ \theta_1 = 45^{\circ} $$ and emerges at an angle $$ \theta_2 = 76^{\circ} $$, as shown in the figure. (a) Determine the refractive index of refraction for the slab. (b) If the light ray enters the plastic at a point $$ L = 50\, cm $$ from the bottom edge, how long does it take the light ray to travel through the slab?