3. A rocket vehicle has an initial total mass of 1250 kg, of which 400 kg is the propellant. Propellant bum provides a steady flow of hot gases at a rate of 20 kg/s. This vehicle is launched from the earth's surface vertically. Assume that the drag force on the vehicle is negligible and the nozzle exhaust pressure approximates the outside pressure during the vehicle's flight. a. What is the required thrust if we want to have an initial acceleration of 4ge? b. What the altitude the vehicle will reach when the propellant bums out? C. Calculate the vehicle's acceleration and velocity at the moment of burnout. [20 Marks]