Included are a judging device configured to judge economic efficiency to be brought by charging and discharging of a storage battery based on a first sale price of electric power in a first time slot, a second sale price of the electric power in a second time slot, and charge/discharge efficiency of the storage battery, the first time slot being obtained by dividing a day into predetermined time periods, the second time slot being obtained by dividing the day into the predetermined time periods and being different from the first time slot; and a determining device configured to determine a charge/discharge plan of the storage battery in the first and the second time slots based on a judgment result of the judging device.
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