The current density in a cylindrical wire of radius r=4.0 mm is 1.0 × 10^6 A / m^2. The current through the outer portion of the wire between radial…

The current density in a cylindrical wire of radius $\displaystyle r=4.0 \mathrm{~mm}$ is $\displaystyle 1.0 \times 10^6 \mathrm{~A} / \mathrm{m}^2$. The current through the outer portion of the wire between radial distances $\displaystyle \frac{r}{2}$ and $\displaystyle r$ is $\displaystyle x \pi \mathrm{~A}$; where $\displaystyle x$ is \_\_\_\_.