Thanks for your help in advance, here's the problem:

The path of a golf ball can be modeled by a quadratic equation. The path of a ball hit an angle of 10 degrees can be modeled by h=-0.002d^2+0.4d where h is the height in meters and d is the horizontal distance the ball travels in meters until it first hits the gorund.

a) What is the maximum height reached by the ball?

The answer is 20m, usually I would just sub in 0 for d to find h but in this case it's different. What should I do?