A spherical shell of radius `R` is given charge `3q` on its surface and a point charge `q` is placed at distance `R//2` from its centre `C`. Also there is a charge `2q` placed outside the shell at a distance of `2R` as shown. Then

Options

A. The magnitude of electric field at the centre `C` due to charge on the outer surface of shell is `(Kq)/(2R^(2))` before closing the switch `S`
B. The electric potential at the centre `C` due to charges on the outer surface of shell is `((-Kq)/R)` before closing the switch `S`
C. The electric potential at the centre `C` due to charges on the outer surface of shell is `((-Kq)/R)` after closing the switch `S`.
D. Charge flown through the switch in to earth after closing the switch `S` is `5q`

Explanation

A, C, D