Two identical small conducting balls \(B _1\) and \(B _2\) are given -7 pC and +4 pC charges respectively. They are brou…

Two identical small conducting balls \(B _1\) and \(B _2\) are given -7 pC and +4 pC charges respectively. They are brought in contact with a third identical ball \(B _3\) and then separated. If the final charge on each ball is -2 pC , the initial charge on \(B_3\) was