A toroid having a square cross section, 4.40 cm on a side, and an inner radius of 13.1 cm has 660 turns and carries a current of 0.801 A. (It is made up of a square solenoid instead of round one bent into a doughnut shape.) What is the magnitude of the magnetic field inside the toroid at
(a) the inner radius and
(b) the outer radius?