A solid conducting sphere of radius \(a\) carries a net positive charge \(+Q\). It is concentric with an uncharged conducting spherical shell with inner radius \(b\) and outer radius \(c\), where \(a < b < c\). The electric potential is defined to be zero at infinity (\(V(\infty) = 0\)). Which of the following graphs best represents the electric potential \(V\) as a function of radial distance \(r\) from the common center?