this topic is from momentum and inertia so it should be solved with those formulas. If possible i need to understand the step by step of it.

Problem 4 A 2-kg object, moving at 1m/s, collides with a 1-kg object that is initially at rest. After the collision, the two objects are found to move away from each other at 1 m/s. Assume they form an isolated system. (a) What are their actual final velocities in the Earth reference frame? (b) What is the velocity of the center of mass of this system? Does it change as a result of the collision