Two trains leave a station at 12:00 noon. One travels north on a track at 75 mph. The second travels east on a track at 30 miles per hour. At 1:00 PM the northbound train stops for one-half hour at a station while the eastbound train continues at 30 miles per hour without stopping. At 1:30 PM the northbound train continues north at 75 mph. How fast are the trains traveling away from one another at 4:00 PM? The distance between the trains is increasing at miles per hour.