You are the mission commander of a 2000kg probe that is approaching Mars at a speed of 25,000 km/hr. It needs to slow down to 15,000 km/hr to begin its descent to the surface. If the satellite enters the Martian atmosphere too fast, it will burn up; if it enters too slowly, it will use up its maneuvering fuel before reaching the surface and will crash. The satellite has a new braking system: several 5.0kg masses on the front that can be launched straight ahead at a speed of 139,000 m/s relative to the satellite. You need to send the rocket an instruction to tell how many bullets to fire. Success will bring you fame and glory, but failure of this $500,000,000 mission will ruin your career. How many bullets?