A solid metallic sphere has a charge `+3Q`. Concentric with this sphere is a conducting spherical shell having charge `-Q`. The radius of the sphere is `a` and that of the spherical shell is `b(bgta)` What is the electric field at a distance `R(a lt R lt b)` from the centre
A. `(Q)/(2piepsilon_(0)R)`
B. `(3Q)/(2piepsilon_(0)R)`
C. `(3Q)/(4piepsilon_(0)R)`
D. `(4Q)/(2piepsilon_(0)R^(2)`
