Answer
$E=6.21\times 10^2\frac{N}{C}$
Work Step by Step
We know that:
$E=\frac{\sigma _A}{2\epsilon_{\circ}}-\frac{\sigma _B}{2\epsilon_{\circ}}$
We plug in the known values to obtain:
$E=\frac{8.00\times 10^{-9}-(-3.00\times 10^{-9})}{2(8.85\times 10^{-12})}$
$E=\frac{8.00\times 10^{-9}+3.00\times 10^{-9}}{2(8.85\times 10^{-12})}=6.21\times 10^2\frac{N}{C}$
