Three Nearly Massless Charges Lie On A Line The Charge Of Q1 Is 5 4 The Charge O

Three nearly massless charges lie on a line. The charge of q1 is +5.4 , the charge of q2 is -2.9 , and the charge of q3 is 6.6 .The distance A is found to be 0.38 meters. What is the distance B where charge q3 experiences no net force?