Solve this 13 problem

. 13 Go In Fig. 21-26. particle 1 of charge + 1.0 uC and particle 2 of charge -3.0 uC are held at separation / 10.0 cm on an x axis. If particle 3 of un- known charge q: is to be located such Figure 21-26 Problems 13. that the net electrostatic force on it 19, 30. 58, and 67. from particles 1 and 2 is zero, what must be the (a) r and (b) v coor- dinates of particle 3