When a point charge of (+q) is placed at corner (A) of a square (see figure), the magnitude of the electric field at the center of the square is found to equal 6.50 x 104 N/C. What is the the magnitude of the electric field at the center of the square when a charge (+q) is placed at corner (A), a charge (+q) is placed at corner (B), a charge (-q) is placed at corner (C), and a charge (+q) is placed at corner (D)?