Two point charges `100 mu C` and `5 mu C` are placed at points `A and B` respectively with `AB = 40 cm`. The work done by external froce in displacing the charge `5 mu C` from B to C, where `BC = 30 cm`, angle `ABC = (pi)/(2)` and `(1)/(4pi epsilon_(0)) = 9 xx 10^(9)Nm^(2)//C^(2)`