The administrative unit shall issue its final order within 90 days after the date of the hearing on exceptions. The administrative unit may affirm, reverse, or modify the proposed order, or may remand the matter with specific instructions to the Office of Administrative Hearings. The administrative unit shall send a copy of the final order to the parties, or if represented by counsel to their attorneys, by first-class mail within 3 business days from the date of the issuance of the final order. The final order or an accompanying letter shall advise the parties of their rights to judicial review of the decision.