Three equal negative point charges of q$=(5\mathrm{.}700$x$10^-9)$ C are placed at three of the corners of a square of side d and a all sides are equal, where d $=0\mathrm{.}042$ m$.$ What is the magnitude of the electric field at point A in the center of the square? Express your answer using two significant figures. Your answer should be in N$/$C$.$