(1) By the end of the 30-day negotiation period described in 90-6-307(6) , MCA, all affected parties shall notify the board in writing of the outcome of their negotiation efforts, specifying which objections have been resolved and how and which objections remain in contention. The developer shall provide the board with any mutually agreed upon amendments to the plan. The official copy of the amendments must bear the signatures of the developer's authorized representative, the chairman of the elected governing body of each affected unit of local government, and the chairman of the elected governing body of the county verifying the concurrence of their units of local government with the negotiated amendments.