A coaxial cable | Mathematics homework help

A Coaxial Cable. A small solid conductor with radius a is supported by insulating. nonmagnetic disks on the axis of a thinwalled tube with inner radius b. The inner and outer conductors carry equal currents i in opposite directions. 
(a) Use Ampere’s law to find the magnetic field at any point in the volume between the conductors. 
(b) Write the expression fur the flux diPB through a narrow strip of length I parallel to the axis, of width dr, at a distance T from the axis of the cable and lying in a plane containing the axis. 
(c) Integrate your expression from part (b) over the volume between the two conductors to find the total flux produced by a current i in the central conductor. 
(d) Show that the inductance of a lenglh I of the cable is
(e) Use Eq. (30.9) to calculate the enetgy stored in the magnetic field for a length l of thecable.