A Toroid Has 200 Turns of Wire with a Current $\times$

Multiple Choice

A toroid has 200 turns of wire with a current of 3 A passing through the wire.The inner radius of the toroid is 3 cm and the outer radius is 5 cm.Calculate the magnetic field strength at a radius of 2 cm.

A) 6.0 $\times$ 10^-3 T
B) 3.0 $\times$ 10^-3 T
C) 1.2 $\times$ 10^-2 T
D) 4.8 $\times$ 10^-4 T
E) none of the above