Two point charges are fixed on the y axis: a negative point charge q1 = -28 µC at y1 = +0.20 m and a positive point charge q2 at y2 = +0.33 m. A third point charge q = +8.7 µC is fixed at the origin. The net electrostatic force exerted on the charge q by the other two charges has a magnitude of 20 N and points in the +y direction. Determine the magnitude of q2.