This isn't a coherence question (or advanced physics) but here goes -
You haven't shown any of your work, so lets break this down and go from the beginning - you should know that the beam of light bends as it passes through the first surface of the prism - you should know of a law that describes how much bending occurs. Then what happens to the beam of light?
73.8 degrees? Not yet. I was only looking for the angle inside the prism, then we were going to go thru and refract again at the second surface. You really need to show your work so I know what you're thinking - that's the way you get partial credit.