Answer:52 seconds5833 feetStep-by-step explanation:Each plane has a starting altitude and a fixed rate of climb. Its altitude at some time t will be the sum of the starting altitude and t times the rate of climb.__plane A altitude = starting altitude + t × rate of climb a(t) = 4000 +35.25tplane B b(t) = 2427 +65.5tsame altitudeThe planes will be at the same altitude at the same time when ... a(t) = b(t) 4000 +35.25t = 2427 +65.5t 1573 = 30.25t . . . . . . . . . . subtract 2427+35.25t 52 = t . . . . . . . . . . . . . divide by 30.25That altitude is ... a(52) = 4000 +35.25×52 = 4000 +1833 = 5833summary52 seconds will pass before the planes are at the same altitude.Their altitude then will be 5833 feet.