Answer
$\sigma=4.5\times10^{-7}\frac{C}{m^2}$
Work Step by Step
We will use the following formula:
$\sigma=\frac{q}{4\pi r^2}$
Putting the values and solving:
$\sigma=\frac{2.4\times10^{-6}}{4\pi(\frac{1.3}{2})^2}$
$\sigma=4.5\times10^{-7}\frac{C}{m^2}$
