The designers of a water park have sketched a preliminary drawing of a new slide. The length of the ladder is l = 15 feet, and its angle of elevation is 60° (see figure). (a) Find the height h of the slide. (Round your answer to two decimal places.)
I got this already, which is 12.99 ft.
(b) Find the angle of depression from the top of the slide to the end of the slide at the ground in terms of the horizontal distance d a rider travels.

(c) Safety restrictions require the angle of depression of the slide to be no less than 25° and no more than 30°. Find an interval for how far a rider travels horizontally. (Round all numerical values to one decimal place. Enter your answer using interval notation.)

I attached the figure.