A charge \(Q\) is distributed over three concentric spherical shell of radii \(a, b, c (a < b < c)\) such that their surface charge densities are equal to one another. The total potential at a point at distance \(r\) from their common centre, where \(r < a\), would be

1. A \(\frac{Q}{{12\pi \,{ \in _0}}}\frac{{ab + bc + ca}}{{abc}}\)
2. B \(\frac{{Q\,\left( {{a^2} + {b^2} + {c^2}} \right)}}{{4\pi \,{ \in _0}\,\left( {{a^3} + {b^3} + {c^3}} \right)\,}}\)
3. C \(\frac{Q}{{4\pi \,{ \in _0}\,\left( {a + b + c} \right)\,}}\)
4. D \(\frac{{Q\,\left( {a + b + c} \right)}}{{4\pi \,{ \in _0}\,\left( {{a^2} + {b^2} + {c^2}} \right)\,\,}}\)