Sections 55304 and 55305 of this title do not apply to export activities of the Secretary of Agriculture or the Commodity Credit Corporation under which—

(1) agricultural commodities or their products acquired by the Corporation are made available to United States exporters, users, processors, or foreign purchasers for the purpose of developing, maintaining, or expanding export markets for United States agricultural commodities or their products at prevailing world market prices;

(2) payments are made available to United States exporters, users, or processors or, except as provided in section 55314 of this title, cash grants are made available to foreign purchasers, for the purpose described in paragraph (1);

(3) commercial credit guarantees are blended with direct credits from the Corporation to reduce the effective rate of interest on export sales of United States agricultural commodities or their products;

(4) credit or credit guarantees for not more than 3 years are extended by the Corporation to finance or guarantee export sales of United States agricultural commodities or their products; or

(5) agricultural commodities or their products owned or controlled by or under loan from the Corporation are exchanged or bartered for materials, goods, equipment, or services at least equal in value to the agricultural commodities or their products for which they are exchanged or bartered (determined on the basis of prevailing world market prices at the time of the exchange or barter), but this paragraph does not exempt from the cargo preference provisions referred to in section 55314(b) of this title any requirement otherwise applicable to the materials, goods, equipment, or services imported under the transaction.