(1) The provisions of this Part of these Regulations shall have effect as the case may require for the purpose of the calculation of the total charge for credit under Part II above and of the rate of such charge under Part III above in relation to any actual or prospective agreement in respect of matters necessary for the calculation which cannot be ascertained by the creditor at the date of the making of the agreement.
(2) In a case where apart from this paragraph regulation 13 below and one or more other provisions of this Part would fall to be applied the said regulation 13 shall be applied first.