A coaxial cable consists of an inner cylindrical conductor of radius R₁ = 0.040 m on the axis of an outer hollow cylindrical conductor of inner radius R₂ = 0.080 m and outer radius R₃ = 0.090 m. The inner conductor carries current I₁ = 1.3 A in one direction, and the outer conductor carries current I₂ = 7.8 A in the opposite direction.

A) What is the magnitude of the magnetic field at the following distances from the central axis of the cable? (µ₀ = 4p × 10^-7 T · m/A)

B) At r = 0.150 m (outside the cable)

At r = 0.060 m (in the gap midway between the two conductors)