The second stage of the two-stage rocket weighs, 2000 lb (empty) and is launched from the first stage with a velocity of 3000 mi/h. the fuel in the second stage weighs 1000 lb. If it is consumed at the rate of 50 lb/s and ejected with a relative velocity of 8000 ft/s, determine the acceleration of the second stage just after the engine is fired. What is the rocket’s acceleration just before all the fuel is consumed? Neglect the effect of gravitation.