Angle of incidence / angle of refraction practice problems

Light travels from diamond into fiber optic cable with an angle of refraction (θr) of 22.8 °. What is the angle of incidence (θi) if the refractive index of diamond is 2.4 and the refractive index of fiber optic cable is 1.6.

The angle of incidence is: ° (Give your answer to the nearest 10th of a degree)