The diagram represents a boy letting out a kite. The boy lets out string at 3 ft/sec, and the wind blows the kite away horizontally at 2ft/sec. At what moment when the kite is 50 feet high and the length of string is 130 feet, find the following:
a) the rate of change of the height of the kite.
b) the rate of change of the area of the triangle.
c) the rate of change of the angle between the string and the ground.