A coaxial cable consists of an inner cylindrical conductor of radius 3 cm on the axis of an outer hollow cylindrical conductor of inner radius 7 cm and outer radius of 10 cm. The inner conductor carries current 4.5 A in one direction, and the outer conductor carries current 8 A in the opposite direction. (a) What is the value of the magnetic field at distances 8 cm and 20 cm from the axis of the cable? (b) Draw how the magnitude of the magnetic field changes with the distance from the axis of the cable.