Final answer:
The net work done by friction is zero when pulling the board directly from region 1 to region 2 at a constant velocity.
Step-by-step explanation:
The net work done by friction in pulling the board directly from region 1 to region 2 can be determined by calculating the work done by each force and then summing them up. Since the board moves at constant velocity, the net work done by friction is zero.
Friction is always opposite to the direction of motion, so the work done by friction is negative. However, in this case, since the board moves at constant velocity, the work done by the pulling force is equal in magnitude and opposite in direction to the work done by friction, making the net work done by friction zero.