An electron initially 3.00 m from a non-conducting infinite sheet of uniformly distributed charge is fired toward the sheet. The electron has an initial speed of 350 m/s and travels along a line perpendicular to the sheet. When the electron has traveled 2.00 m , its velocity is instantaneously zero, and it then reverses its direction.

What is the surface charge density on the sheet?

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