Section 146. Before making such order the attorney general shall hold a public hearing or hearings at which an opportunity to be heard shall be afforded to any employer, or representative of employers, and any industrial homeworker, or representative of industrial homeworkers, and any other person or persons, having an interest in the subject matter of the hearing. At least thirty days before any such hearing is held public notice thereof shall be given in such manner as may be determined by the attorney general. Such hearing or hearings shall be held in such place or places as the attorney general shall deem most convenient to the employers and industrial homeworkers to be affected by such order. The attorney general shall determine the effective date of such order, which date shall be not less than ninety days after the date of its promulgation.