Three thin, concentric conducting spherical shells have radii \(a\), \(b\), and \(c\), where \(a < b < c\). The innermost shell of radius \(a\) and the outermost shell of radius \(c\) are each connected to ground such that their electric potentials are zero (\(V = 0\)). The middle shell of radius \(b\) is connected to a power supply that maintains it at a constant positive electric potential \(V_0\). In terms of the given quantities and fundamental constants, what is the total electric charge \(Q_b\) residing on the middle shell?