An air traffic controller spots two planes at the same altitude converging on a point as they fly at right angles to each other. One plane is 75 miles from the point moving at 300 miles per hour. The other plane is 100 miles from the point moving at 400 miles per hour.
(a) At what rate (in mi/hr) is the distance s between the planes changing?
(b) How much time (in hr) does the controller have to get one of the planes on a different flight path?