9. A 2 kg car moving towards the right at 4 m/s collides head on with an 8 kg car moving towards the left at 2 m/s, and they stick together. After the collision, the velocity of the combined bodies is

A. 0
B. 0.8 m/s towards the right.
C. 0.8 m/s towards the left.
D. 2.4 m/s towards the right.
E. 2.4 m/s towards the left.

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