A hot air balloon rises at the rate of 70 feet per minute. An observer 410 feet from the place of ascent watches the balloon rise.

a) Write an expression for the altitude of the balloon in terms of time, t minutes, and the angle of elevation, theta.

b) What is the altitude of the balloon after 3.5 minutes, 22 minutes, and 1 hour?

c) What are the angles of elevation to the nearest minute for each amount of time?

I can only figure out how to make an equation for a), not an expression. I know how to do b) but I don't know how to get the angles of elevation for each time.