A Conducting Hollow Cylinder (Inner Radius = A, Outer Radius

A conducting hollow cylinder (inner radius = a, outer radius = b) carries a current of 40 A that is uniformly distributed over the cross section of the conductor. If a = 3.0 mm and b = 6.0 mm, what is the magnitude of the (line) integral around a circular path (radius = 5.0 mm) centered on the axis of the cylinder and in a plane perpendicular to that axis?

A) 50 μT ⋅ m
B) 30 μT ⋅ m
C) 22 μT ⋅ m
D) 37 μT ⋅ m
E) 47 μT ⋅ m