The figure shows two coaxial solenoids, the inner one has radius a y with n_a "loops" and the outer one has radius b and n_b "loops", both with currents I, but flowing in opposite directions. Find the magnetic field: i) inside the cylinder of radius a; ii) between the two cylinders; iii) outside the cylinder of radius b

The figure shows two coaxial solenoids, the inner one has radius a y with n_a "loops" and the outer one has radius b and n_b "loops", both with currents I, but flowing in opposite directions. Find the magnetic field: i) inside the cylinder of radius a; ii) between the two cylinders; iii) outside the cylinder of radius b