Answer: The total momentum before the docking maneuver is
and after the docking maneuver is 
Explanation:
Linear momentum
(generally just called momentum) is defined as mass in motion and is given by the following equation:
Where
is the mass of the object and
its velocity.
According to the conservation of momentum law:
<em>"If two objects or bodies are in a closed system and both collide, the total momentum of these two objects before the collision </em>
<em>will be the same as the total momentum of these same two objects after the collision </em>
<em>".
</em>
<em />

This means, that although the momentum of each object may change after the collision, the total momentum of the system does not change.
Now, the docking of a space vehicle with the space station is an inelastic collision, which means both objects remain together after the collision.
Hence, the<u> initial momentum</u> is:

Where:
is the mass of the vehicle
is the velocity of th vehicle
is the mass of the space station
is the velocity of the space station
And the <u>final momentum</u> is:

Where:
is the velocity of the vehicle and space station docked