According To Observer A Two Objects

According to observer A, two objects of equal mass and moving along the x axis collide head on and stick to each other. Before the collision, this observer measures that object 1 move to the right with a speed of 3c/4, while object 2 moves to the left with the same speed. According to observer B, however, object 1 is initially at rest.
(a) Determine the speed of object 2 as seen by observer B.
(b) Compare the total initial energy of the system in the two frames of reference.

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