** A +35.0 nC charge is placed at the origin of a coor- dinate system, and a -25.0 nC charge is placed in the xy-plane at the point (x = 0.100 m, y = -0.0500 m). (a) Determine the magnitude and the direction of the force that the positive charge exerts on the negative charge. Use ijk notation for your result. (b) Determine the magnitude and direction of the force of the negative charge on the positive charge.