3/184 The 15 200-kg lunar lander is descending onto the moon's surface with a velocity of 2 m/s when its retro-engine is fired. If the engine produces a thrust T for 4 s which varies with time as shown and then cuts off, calculate the velocity of the lander when t = 5 s, assuming that it has not yet landed. Gravitational acceleration at the moon's surface is 1.62 m/s?. 2 m/s T, kN 45 t, s Problem 3/184 4. 2.