Two point charges 100µc and 5µc are placed at points A and B respectively with AB = 40 cm. The work done by external force in displacing the charge 5µc from B to C where BC = 30 cm, angle `ABC = pi/ 2` and `1/(4piepsilon_o)=9xx 10^9 Nm^2' /'c^2` .
Options:
(a) 9 J
(b) `9/25J`
(c) `81 /20J`
(d) `-9/4J`