Article 424.

1. The performance of the contract shall be paid at the price specified by the agreement of the parties; in the cases provided for by law, the prices (prices, prices, rates, etc.) fixed or regulated by the 2. Changes in the price after the conclusion of the contract are permitted in the cases and under the terms of the contract, for 3. In cases where the contract of reimbursement does not provide for the price and cannot be determined on the basis of the terms of the contract, the performance of the contract must be paid. The Panel recommends no award of compensation in respect of a price that, in comparable circumstances, is usually charged for similar goods, works or services.