A Projectile with a Mass 6M Is Fired at a Speed

Multiple Choice

A projectile with a mass 6M is fired at a speed of 400 m/s at an angle of 60º above the horizontal.At the highest point of its trajectory,the projectile is broken into two equal pieces by an internal explosion.Just after the explosion,one of the two pieces is known to be traveling vertically downward at a speed of 300 m/s.The magnitude of the velocity of the other half of the projectile is

A) 500 m/s
B) 1.50 km/s
C) 400 m/s
D) 710 m/s
E) 123 m/s