Given,
The mass of object A is

The mass of object B is

The velocity of the object A before the collision is

The velocity of the object B before the collision is

The velocity of object A after the collision is

Let the velocity of object B after the collision is v.
(a) The total initial momentum of objects A and B.

The total initial momentum of objects A and B is 8.
(b) From the conservation of momentum,

The final velocity of object B after the collision is 1 m/s.