An unknown negative point charge is placed at x = -0.49 m, y = 0 m, a charge of -2.5 mico-coulombs is placed at x = 0 m, y = -0.35 m, a charge of +4 micro-coulombs is placed at x = +0.42 m, y = -0.31 m, and charge of +2.5 micro-coulombs is placed at x = 0 m, y = +0.35 m. If the angle of the total electric field due to all four charges is 224.5 degrees measured counter-clockwise from the +x axis, what is the magnitude of the unknown charge?