A transmission device sends status information representing status of a copier to a center through a PSTN. In the center, the status information of each copier is analyzed, and suggestion information selected based on a result of the analysis is provided to a terminal of the user of the copier concerned. In this case, the user is informed by an e-mail or through a Web page with using the terminal. The information includes: a suggestion to multiply the copier, replace the currently-used copier with a new copier, performance information regarding a model of the currently-used copier, information regarding a timing for replenishing/replacing an expendable supply (such as a toner unit, etc.), a suggestion to purchase the expendable supply, and the like.