In a billiards game, the cue ball of mass m travelling with velocity 2.8 m/s in the positive x-direction hits the stationary 9-ball also of mass m. after the collision, the 9-ball moves off at an angle of 30 degrees above the positive x-axis while the cue-ball moves off at an angle of 60 degrees below the positive x-axis. what speed does the cue ball have after the collision? a) 2.8 m/sb) 1.4 m/sc) 0.4 m/sd) 2.4 m/se) 0.7 m/s