1. There shall first be taken an amount (“£a”) which is the greater of the following–
(a)the amount of the charges authorised by sections 78 and 79 of the Act which have been paid to the dental practitioner by the patient in respect of services provided under the contract or arrangement;
(b)the amount of the charges authorised by those sections, including any amount already paid, which would be payable to the dental practitioner by the patient in respect of those services if no charge fell to be made in respect of the supply of the appliance.