Question

A positive point charge +q is fixed in position at the center of a square, as the drawing shows. A second point charge is fixed to corner B, C, or D. The net electric field that results at corner A is zero. (a) At which corner is the second charge located? (b) Is the second charge positive or negative? (c) Does the second charge have a greater, a smaller, or the same magnitude
as the charge at the center? (Justify your answer)