Avery long conductor cyliner of length l and radius r carries a current density along the z-axis given by j(s')=i/s'

a) use ampere's law to find the b field inside and outside the wire in terms of s

if current is removed and replaced by uniform current on the outer surface of cylinder a all along z-axis and parallel to the x-y plane then,
c) use the biot-savart law to calculate the b field inside the cylinder.