Four point charges, q, are fixed to the four corners of a square that is 12.6 cm on a side. An electron is suspended above a point at which its weight is balanced by the electrostatic force due to the four point charges, at a distance of 12 nm above the center of the square. (The square is horizontally flat, and the electron is suspended 12 nm vertically above the center of the square.) What is the magnitude of each fixed charge in coulombs?