If the director finds that the marketing program has been assented to in writing by one of the following, he shall make the marketing program effective:
(a) Not less than 65 percent of the producers in the proration zone that produced for market not less than 51 percent of the quantity of the commodity which was produced in the proration zone in the next preceding season.
(b) Not less than 51 percent of the producers that produced for market not less than 65 percent of the quantity of such commodity which was produced in the proration zone in the next preceding season.