An electron is injected directly towards the centre of a large...

An electron is injected directly towards the centre of a large metal plate having a uniform surface charge density of $-2.0 \times 10^{-6} \mathrm{C} / \mathrm{m}^2$. The initial kinetic energy of the electron is $1.6 \times 10^{-17} \mathrm{~J}$. The electron is observed to stop as it just reaches the plate. Therefore, the distance between the plate and the point from where the electron was injected is