An image forming apparatus changes over an electric potential on an image bearing member in response to an attenuation region in which a remaining potential on a developing member is attenuating after a developing bias applied to the developing member has been turned off after completion of an image forming operations. In one embodiment the bed has a frame, a deck supported on the frame, and a mattress on the deck. The parties send these messages to each others’ client subsystems and to a transaction server, which carries out financial transactions on behalf of the parties.