(a) After a proceeding is commenced and until any cut-off point that the presiding officer may set, any party may serve written interrogatories on any other party. Each interrogatory shall be clear and concise, and, to the degree possible, employ technical terms in the way they are usually employed in commission proceedings; encompass only questions related to each other; and be presented on a separate page. Each party's interrogatories (and document requests pursuant to section 5.4 of this Part) shall be numbered consecutively throughout the proceeding. A copy of every interrogatory shall be served on each party, and on the presiding officer, if he or she so requests.

(b) An individual knowledgeable as to the content of each response to an interrogatory may be required to testify as to its truth or accuracy. If the name of that individual is not set forth on the response, it shall be provided promptly by the responding party upon request.

(c) Except as provided below, a party to whom an interrogatory is directed shall answer each question separately in writing, and shall set forth the question immediately before its answer. Answers shall be served on the requesting party within 10 days following service of the interrogatory, and a copy shall be served on any presiding officer or party who so requests.

(d) If the interrogated party cannot prepare a response within 10 days, it shall, within the 10 days, so inform the interrogating party and state when the response will be forthcoming. Any ensuing dispute over timing of the response shall be submitted to the presiding officer for resolution.

(e) Any objection to an interrogatory shall be made in writing and served on all parties and the presiding officer within 10 days of service of the interrogatory. The interrogatory need not be answered while the objection remains pending. If the presiding officer overrules the objection, the answer to the interrogatory shall be served within five days following the issuance of the ruling or within 10 days following service of the interrogatory, whichever is later.