Answer:
One can use conservation of momentum and energy and obtain the result that the velocity of separation in such a collision will be equal to the velocity of approach
Thus, after collision their speeds will be 3.20 and 1.90 m/s
They will exchange velocities in the collision
If they were approaching each other their relative speeds are
5.10 m/s w.r.t. each other
If they were going in the same direction before the collision their relative speeds before and after the collision are 1.3 m/s
The problem here implies that their relative speed before the collision is 5.10 m/s (traveling in opposite directions)