A ladder 10 ft long leans against a vertical wall. If the lower end is being moved away from the wall at the rate of 6 ft/sec, how fast is the height of the top changing (this will be a negative rate) when the lower end is 6 feet from the wall? The height of the top is changing at a rate of (Simplify your answer.) 10 ft X 10 ft when the lower end is 6 feet from the wall. ft sec ft/sec