An airplane is flying above an observer standing on the ground. At the moment it passes overhead, the observer judges by its apparent size that the airplane’s altitude is 30,000 feet. It takes 50 seconds for the plane, moving in a straight, horizontal line, to move through an angle of 0.94 radians as seen by the observer. The angle described is swept out by the line segment joining the observer to the plane. At this moment, the angle is increasing at a rate of 34.3 radians per hour. What is the speed of the plane at this time, in miles per hour?
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