Any marketing order or amendment thereto directly assessing handlers shall be issued either (1) when the director determines that the issuance of such order or amendment is assented to or favored by handlers who during a representative period determined by the director constituted at least fifty-one percent by numbers or fifty-one percent by volume handled of the handlers who have been engaged in the handling of the commodity specified in such marketing order produced in such production area or marketed in such marketing area, as the case may be, or (2) when upon the basis of findings on a duly noticed hearing held in the manner herein provided, the director determines:

(a) That the issuance of such order or amendment will not result in unequal cost of product or availability of supplies, or cause competitive disadvantage of other respects as between handlers;

(b) That the issuance of such order or amendment is the only practical means of advancing the interest of producers of such commodity pursuant to the declared policy of this chapter and that failure to issue such order or amendment would tend to prevent effectuation of the declared policies of this chapter;

(c) That the issuance of such order is assented to or favored by producers who during a representative period determined by the director constituted at least seventy-five percent by numbers or at least sixty-five percent by volume of production of the producers who have been engaged within the production area specified in such marketing order in the production for market of the commodity specified therein, or who during such representative period have been engaged in the production of such commodity for sale in the marketing area specified in such order.