(a) Notice. Any party, within the time prescribed by §12.30(d), may serve on any other party or any officer or agent of a party a notice of the taking of a deposition on written interrogatories.

(b) Number. The number of written interrogatories served upon any one party shall not exceed thirty. For the purpose of this rule, each sub-interrogatory or divisible part of an interrogatory shall be regarded as one interrogatory. Leave to serve additional interrogatories shall not be granted absent extraordinary circumstances.

(c) Reply.

(1) Each interrogatory served shall be answered by the party served or if the party is a corporation, partnership, association, or government agency, by any officer or agent thereof selected by the responding party.

(2) Each interrogatory shall be answered separately and fully in writing, unless objected to, in which event the reasons for objection shall be stated in lieu of an answer. For the purposes of this rule, an evasive or incomplete answer shall be treated as a failure to answer. The answers are to be signed and verified by the person making them. The person upon whom a notice to take a deposition on written interrogatories has been served shall serve a copy of the answers and objections within twenty (20) days after service of the interrogatories.

(d) Deposition of a non-party. The deposition on written interrogatories of a non-party may be taken only within the time prescribed by §12.30(d), and only pursuant to an order entered and subpoena issued in accordance with the provisions of §12.313 of these rules; provided however, that the deposition on written interrogatories of a Commission member or employee may only be taken upon a showing that the Commission member or employee has personal knowledge of the matters sought to be discovered (i.e., not obtained pursuant to a Commission investigation), that the information sought to be discovered is material and that the information sought to be discovered is not available from other sources.

(e) Filing of depositions on written interrogatories in a voluntary or summary decisional proceeding. In proceedings commenced pursuant to §12.26 (a) and (b) of these rules, copies of all depositions on written interrogatories shall be filed by the party on whose behalf the discovery was obtained.