9. A battleship is moving forward at 20 m/s. A cannonball is fired backward from the ship at 100 m/s relative to the ship. If forward is positive, what is the velocity of the cannonball for an observer on a stationary ship next to the battleship? a) (+120 m/s) X (+80 m/s)X (-120m/s)X d) (-80 m/s) X e) Not enough information to determine