JEE Main 2022 · 27 Jun · Shift 2, Physics question 56

The current density in a cylindrical wire of radius $r=4.0$ mm is $1.0\times10^6$ A/m$^2$. The current through the outer portion of the wire between radial distances $\dfrac r2$ and $r$ is $x\pi$ A; where $x$ is ______.