(Q3) (based on Prob 21.41) If two electrons are each 1.50 X 10'\" m from a proton (see figure below), find the net electric force they will exert on the proton. Express the net force in terms of the standard unit vectors '1' and j. (Q4) (based on Prob P21.7l) Three identical point charges q (> O) are placed at each of three corners of a square of side L. Find the magnitude and direction of the net force on a point charge 3q placed (a) at the center of the square and (b) at the vacant corner of the square