an antidumping or countervailing duty proceeding under this title, the administering authority may use any reasonable method and is not bound by the determinations of any other Federal agency, including tariff classification and country of origin marking rulings issued by the Commissioner of U.S. Customs and Border Protection. (b) Class or kind of merchandise For purposes of this title, determinations regarding whether merchandise is the same class or kind may be made under this section or under section 781 in accordance with the criteria set forth in this section or in section 781, as the case may be. (c) Origin of merchandise To determine the origin of merchandise for purposes of an antidumping or countervailing duty proceeding under this title, the administering authority may apply any reasonable method and may consider relevant factors, including— (1) whether the processed downstream product is a different class or kind of merchandise than the upstream product