What condition must be met before the Authority can enter into a contract exceeding a certain value, as per section 21 of the the Airports Authority of India Act?

Contracts exceeding a specified value must be previously approved by the Authority, Explanation: : Section 21. Mode of executing contracts on behalf of the Authority: (1) Every contract shall, on behalf of the Authority, be made by the Chairperson or such other member or such officer of the Authority as may be generally or specially empowered in this behalf by the Authority and such contracts or class of contracts as may be specified in the regulations shall be sealed with the common seal of the Authority: Provided that no contract exceeding such value or amount as the Central Government may, from time to time, by order, fix in this behalf shall be made unless it has been previously approved by the Authority.