(a) General. At any time after the filing of the first responsive pleading or motion that delays the filing of an answer, such as a motion to dismiss, any party may serve interrogatories upon any other party. The number of interrogatories shall not exceed 25 questions, including subparts, without an order of the Commission or Judge. The party seeking to serve more than 25 questions, including subparts, shall have the burden of persuasion to establish that the complexity of the case or the number of citation items necessitates a greater number of interrogatories.
(b) Answers. All answers shall be made in good faith and as completely as the answering party's information will permit. The answering party is required to make reasonable inquiry and ascertain readily obtainable information. An answering party may not give lack of information or knowledge as an answer or as a reason for failure to answer, unless he states that he has made reasonable inquiry and that information known or readily obtainable by him is insufficient to enable him to answer the substance of the interrogatory.
(c) Procedure. Each interrogatory shall be answered separately and fully under oath or affirmation. If the interrogatory is objected to, the objection shall be stated in lieu of the answer. The answers are to be signed by the person making them and the objections shall be signed by the party or his counsel. The party on whom the interrogatories have been served shall serve a copy of his answers or objections upon the propounding party within 30 days after the service of the interrogatories. The Judge may allow a shorter or longer time. The burden shall be on the party submitting the interrogatories to move for an order with respect to any objection or other failure to answer an interrogatory.