Third. Four. c) The full price to be paid, inclusive of tax, where applicable breaking down the amount of surcharges or discounts applicable to the offer and any additional costs passed on to the consumer or user. In all other cases where, owing to the nature of the good or service, an exact price cannot be put on the commercial offer, information must be provided on the basis of the calculation to enable the consumer or user to estimate the price. Likewise, when additional costs passed on to consumers or users cannot, for objective reasons, be calculated beforehand, the existence of these additional costs must be stated and, if known, their estimated amount.