Please answer clearly, thanks!

4) To alter the direction of a spacecraft, rockets can be fired briefly in a direction perpendicular to its original motion. (a) If a spacecraft has a total mass of 3480 kg with an initial speed of 105 m/s and the rocket gases are expelled at a speed of 1550 m/s, how much mass must be expelled for a deviation of 35.0 ? (b) What percentage of the total mass was expelled