A projectile of mass m is fired from the ground with an initial speed vi at an angle of q above the horizontal. At the highest point of its arc, it explodes into three pieces, A, B and C, all of equal mass. Immediately after the explosion, pieces A and B are still moving with the same speed as the whole projectile had right before the explosion. However, A is moving vertically downward, and B is moving horizontally forward (i.e. in the same direction as the projectile prior to its explosion). Find the velocity of C right after the explosion.