on which good or service is added to the list. (C) For any good or service included in a list under this paragraph, the Secretary shall specify the allowable margin by which the price at which a person sells or offers for sale such good or service may exceed the average price at which the good or service was sold or offered by the person during the 90-day period prior to the date on which the emergency or disaster involved was declared. (c) Duration of prohibition The prohibition described in subsection (a) shall apply to a good or service that is included on a list published by the Administrator or the Secretary (as applicable) under subsection (b)— (1) beginning with the first day that the good or service is included on such a list