The respondent shall file with the Commission an answer within twenty-five (25) days of service of the complaint and shall serve a copy of said answer upon complainant. The answer shall admit or deny each matter set forth in the complaint. Matters not specifically denied will be deemed admitted. Where matters are urged in defense, the answer shall be accompanied by appropriate affidavits, other documents, and memoranda. [Rule 312.] [49 FR 44369, Nov. 6, 1984; 49 FR 47394, Dec. 4, 1984]