Magnet a has twice the magnetic field strength of magnet b and at a certain distance pulls on magnet b with a force of 100 n. the amount of force that magnet a exerts on magnet b is

The correct answer is 100 N.

In fact, the problem already says that the force exerted by magnet A on magnet B is exactly 100 N. The information about the magnetic field intensity of the two magnets is redundant, because we are interested only in the magnitude of the force.