The force is not pulling in the direction that the box is moving.
Only the force in the horizontal direction does work.
The force in the vertical direction doesn't do any work, because
the box doesn't move through any vertical distance.
The horizontal force is 200(cos 45°) = 142 newtons
The vertical force is 200(sin 45°) = 142 newtons
If you pull the box 5 meters, then the amount of work done is
(force) x (distance) = (142 N) x (5 m) = 710 joules.
Power = (work done) / (time to do the work)
= (710 joules) / (5 seconds) = 142 watts .
