A point charge `q` is placed inside a conducting spherical shell of inner radius `2 R` and outer radius `3 R` at a distance of `R` from the center of the shell. Find the electric potential at the center of the shell.
A. `(1)/(4 pi epsilon_0) q/(2 R)`
B. `(1)/(4 pi epsilon_0) (4 q)/(3 R)`
C. `(1)/(4 pi epsilon_0) (5 q)/(6 R)`
D. `(1)/(4 pi epsilon_0) (2 q)/(3 R)`