A 1000-Turn Toroid Has a Central Radius of 4

Multiple Choice

A 1000-turn toroid has a central radius of 4.2 cm and is carrying a current of 1.7 A. The magnitude of the magnetic field along the central radius is

A) 8.1 × 10^-3 T.
B) 5.1 × 10^-2 T.
C) 1.6 × 10^-2 T.
D) 8.1 × 10^-2 T.
E) 0.