A long, hollow, cylindrical conductor (inner radius 2.0 mm, outer radius 4.0 mm) carries a current of 24 A distributed uniformly across its cross section. A long thin wire that is coaxial with the cylinder carries a current of 24 A in the opposite direction. What is the magnitude of the magnetic field?

(a) 1.0 mm,

(b) 3.0 mm, and

(c) 5.0 mm from the central axis of the wire and cylinder