Chapter 19 - Electric Charges, Forces, and Fields - Problems and Conceptual Exercises - Page 686: 67

$6.2\times 10^{-6}\frac{C}{m^2}$

We know that $EA=\frac{\sigma A}{\epsilon_{\circ}}$ $\implies \sigma=\epsilon_{\circ}E$ We plug in the known values to obtain: $\sigma=(8.55\times 10^{-12})(7.0\times 10^5)$ $\sigma=6.2\times 10^{-6}\frac{C}{m^2}$