A fireworks shell of mass 9 kg is launched vertically. When it is going 10 m/s upward, the shell splits into three pieces of equal mass. One piece is moving downward at 4 mls and a second piece is moving downward at 12 mls. What is the velocity (magnitude and direction) of the third piece? (Note: Ignore the force of gravity on the object. You are only looking at the moment before and after the explosion so you can get away with this)