For supply or service contracts that meet a regular need, the estimated value of the need is determined on the basis of:
1° Either the amount, excluding taxes, of the services performed during the previous twelve months or the previous financial year, taking into account any changes in the need that may occur during the twelve months following the conclusion of the contract;
2° Or the estimated value of the services that will be performed during the twelve months or the financial year following the conclusion of the contract.