(a) Any party may serve upon any other party written interrogatories after the notice of hearing has been filed. If the party served is a corporation, partnership, association, or governmental agency, an agent shall furnish such information as is available to the party.

(b) Each interrogatory shall be answered separately and fully in writing under oath, unless it is objected to, in which event the objection shall be stated in lieu of an answer. The answers are to be signed by the person making them, and the objections signed by the attorney or other representative making them. Answers and objections shall be made within 30 days after the service of the interrogatories. The party submitting the interrogatories may move for an order under §4.831 with respect to any objection to or other failure to answer an interrogatory.

(c) Interrogatories shall relate to any matter not privileged which is relevant to the subject matter of the hearing.