We know that the electromagnet is a type of magnet whose magnetic property depends on the interaction of the magnetic material with an electric field. We can see in the image that the nail which serves as the magnetic material is connected to a cell which is the source of the given electric current.
It the follows that the nail above is the source of the magnetic force because the coils of wire while the battery cell is the source of the electrical force.
I believe the answer would be -91 because if u solve both of the equations then the f(x) would be 7 and the g(x) would be -13 so it would be 7(-13) which equals -91.