A plane square sheet of charge of side 0.5 m has uniform surface charge density. An electron at 1 cm from the centre of the sheet experiences a force of \( 1.6 \times 10^{-12} \) N directed away from the sheet. The total charge on the plane square sheet is (\( \epsilon_0 = 8.854 \times 10^{-12} \text{ C}^2\text{m}^{-2}\text{N}^{-1} \))