Within twenty-five (25) days after date of service of the complaint, unless a shorter period is fixed, each respondent shall, if it consents to the shortened procedure provided in this subpart, serve upon complainant pursuant to subpart H of this part an answering memorandum of the facts, subscribed and verified according to Sec. 502.112, and of arguments, separately stated, upon which it relies. The original of the answering memorandum shall be accompanied by a certificate of service as provided in Sec. 502.114 and shall be accompanied by copies for the Commission's use. If the respondent does not consent to the proceeding being conducted under the shortened procedure provided in this subpart, the matter will be governed by subpart E of this part and the respondent shall file an answer under Sec. 502.64. [Rule 183.]