An air traffic controller spots two planes at the same altitude converging on a point as they fly at right angles to each other (see figure). One plane is 225 miles from the point, moving at 450 miles per hour. The other plane is 300 miles from the point, moving at 600 miles per hour.

(a) At what rate is the distances between the planes decreasing?

(b) How much time does the air traffic controller have to get one of the planes on a different flight path?