(a) Service and contents. In the interest of expedition and limited to information which appears reasonably calculated to lead to the discovery of admissible evidence, any participant in a proceeding may propound to any other participant no more than a total of 25 written, sequentially numbered interrogatories, by witness, requesting non-privileged information relevant to the subject matter of the proceeding. An interrogatory with subparts that are logically or factually subsumed within and necessarily related to the primary question will be counted as one interrogatory. The respondent shall answer each interrogatory and furnish such information as is available. The participant propounding the interrogatories shall file them with the Commission in conformance with part 3010, subpart B, of this chapter. Follow-up interrogatories that clarify or elaborate on the answer to an earlier discovery request may be filed after the period for intervenor discovery on the Postal Service case ends, if the interrogatories are filed within seven days of receipt of the answer to the previous interrogatory. In extraordinary circumstances, follow-up interrogatories may be filed not less than six days prior to the filing date for the participant's rebuttal or surrebuttal testimony.

(b) Answers. (1) Answers to interrogatories shall be prepared so that they can be incorporated into the record as written cross-examination. Each answer shall begin on a separate page, identify the individual responding and the relevant testimony number, if any, the participant who propounded the interrogatory, and the number and text of the question.

(2) Each interrogatory shall be answered separately and fully in writing by the individual responsible for the answer, unless it is objected to, in which event the reasons for objection shall be stated in a motion to be excused from answering in the manner prescribed by paragraph (c) of this section.

(3) An interrogatory otherwise proper is not necessarily objectionable because an answer would involve an opinion or contention that relates to fact or the application of law to fact.

(4) Answers filed by a respondent shall be filed in conformance with subpart B to part 3010 of this chapter within seven days of the filing of the interrogatories or within such other period as may be fixed by the Commission or presiding officer. Any other period fixed by the Commission or presiding officer shall end before the conclusion of the hearing.

(c) Motion to be excused from answering. A respondent may, in lieu of answering an interrogatory, file a motion pursuant to § 3020.105(b) to be excused from answering.

(d) Supplemental answers. A respondent has a duty to timely amend a prior answer if it obtains information upon the basis of which it knows that the answer was incorrect when made or is no longer true. A respondent shall serve supplemental answers to update or to correct responses whenever necessary, up until the date the answer could have been accepted into evidence as written cross-examination. A respondent shall indicate whether the answer merely supplements the previous answer to make it current or whether it is a complete replacement for the previous answer.