I need a help ... pls help me?

Question

long coaxial cable consists of two concentric conductors with dimensions a = 2.00 cm, b = 4.60 cm and c = 6.90 cm. There are equal and opposite currents of 1.00 A in the conductors. Find the magnitude of the magnetic field at a distance of 0.60 cm from the center axis.

the figure : http://www5.0zz0.com/2008/07/18/12/758359085.gif

Answer 1

donno