A circular conductor, with cross section given by $(x-d)^2+y^2=b^2$, i.e. radius $b$ and centered on $x=d$, has a circular core, made up of the interior of the circle $x^2+y^2=a^2$, with $b-d>a$, removed. A total current $I$ flows in the region between these two circles, with a uniform density, $J$ per unit area. By considering the magnetic field generated by a current density $J$ inside the circle $(x-d)^2+y^2=b^2$ and that generated by an equal and opposite current density in the circle $x^2+y^2=a^2$, show that the magnetic field inside the circle $x^2+y^2=a^2$ is constant with magnitude $\mu_0Id/(2\pi(b^2-a^2))$. In which direction does it point?
I am having trouble understanding the setup of the above described situation. This is how I am interpreting it but I doubt it is right since the situation isn't very symmetrical. I also don't know what it means when it says the region $x^2+y^2=a^2$ with $a < b - d$ is removed.
