To get a uniform field in the central region between the coils, current flows in the same direction in each.
We use the work formula to solve for the unknown in the problem. The formula for work is expressed as the product of the net force and the distance traveled by the object. We were given both the force and the distance so we can solve work directly.
Work = 250 N x 50 m = 12500 J
Thus, the answer is C.
You would expect to find the center of gravity in a ruler in the middle because if you were to cut a ruler in half, depending on the center of gravity, you would have two equal pieces, which mean there is equal weight, meaning the middle is the center of gravity