After consideration of the testimony and other evidence, the administrative unit shall issue a written final order setting forth an appropriate disposition agreed to by a majority of the members of the unit who participated in the hearing. A member who was not present at all parts of the hearing may not vote on the disposition. The final order shall be issued within 90 days after the record of the proceeding is closed unless the administrative unit gives written notice to the parties that the time limit has been extended. The final order shall be signed by the presiding officer or a designee, and unless otherwise noted in the order, is final upon issuance. A copy of the decision shall be maintained in the files of the administrative unit. Decisions issued by an administrative unit in connection with a particular proceeding shall be mailed to the parties, or if represented by counsel to their attorney, by first-class mail within 3 business days from the date of the issuance of the order.