161—9.9 (216) Interrogatories.
	 9.9(1) Availability; procedures for use. The commission may serve written interrogatories to be answered by a party or, if the party from whom the information is sought is a public or private corporation or a partnership or association or governmental agency, by any officer or agent, who shall furnish such information as is available to the party.
Each interrogatory shall be followed by a reasonable space for insertion of the answer. An interrogatory which does not comply with this requirement shall be subject to objection. The interrogatories must be accompanied by a written notice informing the person to whom the interrogatories are directed that a response is mandatory and that sanctions can be levied for a failure to respond.
Each interrogatory shall be answered separately and fully in writing under oath, unless it is objected to, in which event the reasons for objection shall be stated in lieu of an answer.
A party answering interrogatories must answer in the space provided or must set out each interrogatory immediately preceding the answer to it. A failure to comply with this rule shall be deemed a failure to answer and shall be subject to sanctions as provided in rule 161—9.16(216). Answers are to be signed by the person making them. Objections, if any, shall be served within 30 days after the interrogatories are served. The commission may move for an order under subrule 9.16(1) with respect to any objection to or other failure to answer an interrogatory.
The commission shall not serve more than 30 interrogatories on any party under the authority of this rule except upon agreement by the person from whom information is sought or leave of the presiding officer for discovery granted upon a showing of good cause. A motion for leave to serve more than 30 interrogatories must be in writing and shall set forth the proposed interrogatories and the reasons establishing good cause for their use.
Notwithstanding the provisions of this subrule the commission may, without limitation on the number of questions, solicit information from the parties in the form of a written questionnaire. The response to these questions, however, cannot be compelled under rule 161—9.16(216).
	 9.9(2) Scope. An interrogatory otherwise proper is not necessarily objectionable merely because an answer to the interrogatory involves an opinion or contention that relates to fact or the application of law to fact, but the presiding officer for discovery may order that such an interrogatory need not be answered until a later time.
	 9.9(3) Option to produce business records. Where the answer to an interrogatory may be derived or ascertained from the business records of the party upon whom the interrogatory has been served or from an examination, audit or inspection of such business records, or from a compilation, abstract or summary based thereon, and the burden of deriving or ascertaining the answer is substantially the same for the commission as for the party served, it is a sufficient answer to such interrogatory to specify the records from which the answer may be derived or ascertained and to afford to the commission reasonable opportunity to examine, audit or inspect such records and to make copies, compilations, abstracts or summaries. A specification shall be in sufficient detail to permit the commission to locate and identify as readily as can the party served, the records from which the answer may be ascertained.