A Coaxial Wire Consists of a Copper Wire of Radius

Multiple Choice

A coaxial wire consists of a copper wire of radius 1 mm surrounded by a copper sheath of inside radius 1.5 mm and an outside radius 2 mm.A 3-A current flows in one direction down the core and in the opposite direction down the sheath.What is the magnitude of the magnetic field at a radius of 3 mm from the center of the wire?

A) 0 T
B) 1.25 µT
C) 3.15 µT
D) 4.20 µT
E) 5.15 µT