I don't remember how to do this problem. Can someone walk through it once so that I can refresh myself? Thanks!!

Height of Cloud Cover To measure the height of cloud cover at an airport, a worker shines a spotlight upward at an angle of 75 degrees from the horizontal. An observer 600 m away measures the angle of elevation to the spot of light to be 45 degrees. Find the height h of the cloud cover.

My book doesn't cover anything on how to do this and I don't remember when my instructor did it on the board. Thanks.........