Compute all parts of given problem:
Problem: A 115mg plastic bead has a radius of 364um and is charged by the addition of 1.56 x 1010 excess electrons. You may assume that the excess electrons are spread uniformly throughout the bead.
Part A: What is the charge density of the bead?
Part B: What electric field strength will cause the bead to hang suspended in the air?
Please show all intermediate steps and formulas for above problem.