A total current of 23 mA flows through an infinitely long cylinderical conductor of radius 4 cm which has an infinitely long cylindrical hole through it of diameter r centered at r/2 along the x-axis as shown.
What is the magnitude of the magnetic field at a distance of 19 cm along the positive x-axis? The permeability of free space is (4 ×10-7 T · m/A). Assume the current density is constant throughout the conductor.