Problem 2 (5 pts): There is a square ring of positive charge (i.e., line charge of uniform density pi) with side length of a located in the xy-plane with its center at the origin. Calculate the electric field E at a height of h on the z-axis. Problem 3 (5 pts): A sphere of charge of radius a centered at the origin has volume charge density Po = po 1- where po is some constant. The sphere is surrounded by another spherical shell with inner radius r; and outer radius ro. ri > a. Determine E everywhere in space.