Question 65 of 276

A coaxial cable consists of an inner wire of radius $a$ surrounded by an outer shell of inner and outer radii $b$ and $c$ respectively. The inner wire carries an electric current ${i}_{0}$ which is distributed uniformly across cross-sectional area. The outer shell carries an equal current in opposite direction and distributed uniformly. What will be the ratio of the magnetic field at a distance $x$ from the axis when $\left(i\right)$ $x\lt a$ and $\left(ii\right)$ $a\lt x\lt b$ ?