The path of a plane causes it to pass directly over two radar stations, A and B, which are one mile apart. When the plane is on one side of the two stations, and closest to station B, the angle of elevation from radar station A to the plane is 30 and growing at 3 per second, and the angle of elevation from radar station B to the plane is 45 degrees and growing at 4 per second. Find the speed of the plane to the nearest mile per hour