(b) A distributors' bargaining agency may be organized by the distributors in a marketing area. The voting power of each distributor in such bargaining agency shall be in proportion to the quantity of milk distributed by him in such area. Such quantity shall be determined by that distributed during the preceding year as reported to the commissioner. In the New York metropolitan milk marketing area the voting power of each distributor shall be on the basis of one vote for each ten million pounds of milk distributed in such market during the preceding year and in case of a distributor handling a less quantity of milk, a proportionate fractional vote. In other marketing areas the voting basis shall be one vote for each one hundred thousand pounds distributed during the preceding year in such market with a proportionate fractional vote in case of distributors handling a less quantity of milk. The purpose of distributors' bargaining agencies is to negotiate with producers' bargaining agencies as to the agreements or the basis of orders in the respective marketing areas for presentation to the commissioner for his consideration and approval, as provided in section two hundred fifty-eight-m herein. A distributors' bargaining agency may appear before and negotiate with the commissioner in regard to marketing agreements or orders, as provided in section two hundred fifty-eight-m herein. Producers' bargaining agencies and distributors' bargaining agencies may also meet and negotiate in order to carry out the purposes of this act and subject to the approval of the commissioner, as provided in section two hundred fifty-eight-m, may make marketing agreements with each other and with cooperative associations in relation to the marketing of milk which may be handled or distributed in more than one marketing area. Such agencies may also meet and negotiate and take such reasonable measures as are necessary and advisable to cooperate with the commissioner and legally constituted authorities of other states and of the United States with respect to the handling and control of milk handled in interstate commerce and carry out and effectuate the provisions of section two hundred fifty-eight-n. Except as specifically provided in section two hundred fifty-eight-m, the activities and operations of producers' bargaining agencies and distributors' bargaining agencies and of the constituent members thereof, and contracts, agreements or arrangements made by them, pursuant to the provisions of this subdivision, and of section two hundred fifty-eight-m hereof, shall not be deemed or construed to be conspiracies, combinations, contracts or agreements in restraint of trade or commerce or an illegal monopoly. "Milk production area" as used in this article means those dairy farms maintained primarily as a source of fluid milk for a marketing area. Such primary source of supply shall include farms from which all shipments of milk have been subject to the minimum uniform price provisions of a marketing order or agreement for such market during at least a portion of the preceding two years, together with such other farms as may hereafter be designated by the commissioner as a source of supply for the marketing area in the manner prescribed by section two hundred fifty-eight-j.