A spherical capacitor consists of a solid conducting sphere of radius \(a\) surrounded by a concentric conducting spherical shell of inner radius \(b\). The space between the conductors (\(a < r < b\)) is filled with a non-uniform dielectric material whose dielectric constant varies radially according to \(\kappa(r) = \kappa_0 \dfrac{a}{r}\), where \(\kappa_0\) is a dimensionless constant. Which of the following expressions represents the capacitance of this capacitor?