An uncharged, hollow spherical conducting shell has inner radius \(a\) and outer radius \(b\). A small object carrying a positive charge \(+Q\) is suspended on an insulating thread and positioned at the center of the cavity. While the charged object remains at the center, the outer surface of the shell is momentarily connected to ground and then disconnected. After the charged object is completely removed from the cavity without touching the shell, what are the final net charges on the inner surface and outer surface of the shell?