An electron is fired toward a nonconducting infinite sheet carrying a uniformly distributed charge from 5.00 \(\mathrm{m}\) away. The electron has an initial speed of \(3 \times 10^{6} \mathrm{~m} / \mathrm{s}\) along a line perpendicular to the sheet. The electron reverses its motion when it is \(2.00 \mathrm{~m}\) away from the sheet.

(a) What is the surface charge density on the sheet?

(b) Given the same initial velocity, from what distance should the electron be fired if it is to just reach the sheet?