(a) The interrogatories and the response thereto shall not be filed with the court.
(b) The propounding party shall retain both the original of the interrogatories, with the original proof of service affixed to them, and the original of the sworn response until six months after final disposition of the action. At that time, both originals may be destroyed, unless the court on motion of any party and for good cause shown orders that the originals be preserved for a longer period.