Problem about momentum

A 4.0 kg mass is moving at 3.0 meters per second toward the right and a 6.0 kg mass is moving at 2.0 meters per second toward the left on a horizontal frictionless table. I the two masses collide and remain together after the collision, their final momentum is????
let the right side is the positive side
m1=4, v1=3, m2=6, v2=-2
m1v1+m2v2
=4*3+6*(-2)
=0 kg*m/s
Since the momentum does not change before and after the collision
Their final momentum is 0 kg*m/s

2007-01-22 12:35:15 補充：
This is the reason why the two masses collide and remain together (rest !) after the collision