I need help on part C

When granular materials fall, they form conical piles. The angle of slope, measured from the horizontal. at which the material comes to rest is called the angle of repose. The angle of repose is related to the height h and base radius r of the I' conical pile by the equation 8 = not _1 h' When certain granular materials are stored in a pile 16 feet high, the diameter of the base of the pile is 65 feet. (a) Find the angle of repose for these granular materials. B = 2621 (Round to two decimal places as needed.) (b) What is the base diameter of a pile that is 19 feet high? k diameter= 77191 feet (Round to two decimal places as needed.) a (c) What is the height of a pile that has a base diameter of approximately 100 feet? height = D feet (Round to two decimal places as needed.)