This section applies only in Prince George’s County. The county planning board shall approve or disapprove a preliminary subdivision plan within 70 days after the complete plan application is submitted to the county planning board. If the county planning board does not take action in accordance with paragraph (1) of this subsection: the plan shall be considered approved; and the county planning board shall issue a certificate of approval on demand. The 70–day time period under paragraph (1) of this subsection does not include: the month of August; or December 20 through January 3. Each office to which the county planning board refers a preliminary subdivision plan shall return to the county planning board one copy of the plan and any comments noted on it within 30 days after the referral. If an office does not reply in accordance with paragraph (1) of this subsection, the plan shall be considered to be approved by the office. An applicant may consent to an extension not greater than 70 days.