A 5.0-kg mass with an initial velocity of 4.0 m/s, east collides with a 4.0-kg mass with

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A 5.0-kg mass with an initial velocity of 4.0 m/s, east collides with a 4.0-kg mass with an initial velocity of 3.0 m/s, west. After the collision the 5.0-kg mass has a velocity of 1.2 m/s, south. What is, the magnitude of the velocity of the 4.0-kg mass after the collision?