Every final order or decision rendered by any agency in a contested case shall be in writing or stated in the record and shall be accompanied by findings of fact and conclusions of law. Prior to the rendering of any final order or decision, any party may propose findings of fact and conclusions of law. If proposed, all other parties shall be given an opportunity to except to such proposed findings and conclusions, and the final order or decision shall include a ruling on each proposed finding. Findings of fact, if set forth in statutory language, shall be accompanied by a concise and explicit statement of the underlying facts supporting the findings. A copy of the order or decision and accompanying findings and conclusions shall be served upon each party and his attorney of record, if any, in person or by registered or certified mail.