By July 10, 1972, the boards of supervisors of those counties eligible to become member counties of the Bienville Recreational District shall hold a public hearing at their respective courthouses or at some other appropriate hearing rooms whereby local citizens may have the opportunity to express their sentiments on the question of the county's becoming a member and a participant in the activities and objectives of the district. If a board of supervisors finds and determines that public sentiment substantially favors the purposes contained in this chapter, the board shall adopt a resolution declaring its intentions to become a member county of the Bienville Recreational District.