Use the Following Figure to Answer the Next Problem $\pi$ $\times$

Multiple Choice

Use the following figure to answer the next problem:
-The tightly wound toroid shown consists of 100 turns of wire,each carrying a current I = 3 A.If a = 12 cm and b = 15 cm,the magnetic field at r = 18 cm,due to the current in this toroid,is (µ₀ = 4 $\pi$ $\times$ 10^-7 N/A²)

A) 333 µT
B) 400 µT
C) 500 µT
D) 600
E) zero