JEE Main 27-Aug-2021 Shift 2 Solved Paper

A co-axial 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 i0, 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 (i) x < a and (ii) a < x < b ?