(1) An agency shall maintain an official record of each contested case under the Administrative Procedure Act for at least four years following the date of the final order.
(2) The agency record shall consist only of:
(a) Notices of all proceedings;
(b) Any pleadings, motions, requests, preliminary or intermediate rulings and orders, and similar correspondence to or from the agency pertaining to the contested case;
(c) The record of the hearing before the agency, including all exhibits and evidence introduced during such hearing, a statement of matters officially noticed by the agency during the proceeding, and all proffers of proof and objections and rulings thereon; and
(d) The final order.
(3) Except as otherwise provided by law, the physical custody of the agency record shall be maintained by the agency. The agency shall permit the parties to inspect the agency record and obtain copies of the agency record.
(4) Except as otherwise provided by law, the agency record shall constitute the exclusive basis for agency action in contested cases under the act and for judicial review thereof.