The question doesn't ask about anything in particular. I'll compute the net force as a guide, so you can solve your own problem.
Answer:
The net force is zero
Explanation:
Net Force
If we want to compute the net force exerted on a body, we must add them as vectors, i.e. the horizontal and vertical components independently.
The box has 4 forces, as follow
40 N right
40 N left
10 N up
10 N down
The vertical forces are equal and opposite, i.e. their sum is zero. The same situation happens in the horizontal direction, both forces are of equal magnitude and opposite, their sum is zero. The net force is then, zero in both axes
