Answer Happy

I only need the exact answer. Thank you.
a - - Consider a coaxial cable as shown in the figure. The cable consists of a solid inner conductor of radius ri = 0.3 cm that is surrounded by a cylindrical tube of inner radius r 2 0.7 cm and outer radius r3 = 1.8 cm. The conductors carry equal and opposite currents I = 5 A but the current density varies linearly with the distance from the center for the inner conductor (j1 = cir) while it is distributed uniformly for the outer conductor. Determine the magnetic field (in units of uT (microtesla)) at a distancer 1.2 cm from the axis. (uo = 41 x 10-7N/A2 and 7 = 3.14) - Answer: 2 13