Depositions for use at a hearing may, with the consent of the parties in writing or the written approval of the hearing examiner, be taken by either the Director General or the respondent or their duly authorized representatives. Depositions may be taken upon oral or written interrogatories. There shall be at least 10 days written notice to the other party. The requirement of a 10-day written notice may be waived by the parties in writing. When a deposition is taken upon written interrogatories, any cross-examination shall be upon written interrogatories. Copies of such written interrogatories shall be served upon the other party with the notice, and copies of any written cross-interrogation shall be mailed or delivered to the opposing party at least 5 days before the date of taking the depositions, unless the parties mutually agree otherwise. Expenses in the reporting of depositions shall be borne by the party at whose instance the deposition is taken.