the top of a 25-foot ladder is sliding down a vertical wall at a constant rate of 3 feet per minute. when the top of the ladder is 7 feet from the ground, what is the rate of change of the distance between the bottom of the ladder and the wall? (a) 7 8 feet per minute (b) 7 24 feet per minute (c) 7 24 feet per minute (d) 7 8 feet per minute (e) 21 25 feet per minute