An electric point charge of Q1 = 9.15 nC is placed at the origin of the real axis. Another point charge of Q = 4.87 nC is placed at a position of p = 2.13 m on the real axis. At which position can a third point charge of q = -4.19 nC be placed so that the net electrostatic force on it is zero? Let the sign of Q2 be changed from positive to negative. At which position can the point charge q be placed now so that the net electrostatic force on it is zero?