An airport traffic control tower is responsible for all airplanes within a 75-mile radius. A flight takes off from Austin at 5:00 AM and flies directly to Seattle, passing over Salt Lake City in the process. The distance from Salt Lake City to Seattle is 800 miles, the distance from Austin to Seattle is 2000 miles, and the airplane arrives in Seattle at 9:00 AM. Assuming the airplane travels at a constant speed, when is the air traffic control tower in Salt Lake City responsible for the airplane? Disregard any time zone changes