N.Y. General City Law § 131: Letting of contract to be public

§ 131. Letting of contract to be public. Every such contract shall be

let at public letting as required by law, and as a consideration for the

execution and performance thereof, shall expressly provide for and

secure to such city, prices lower than any now prescribed therein by

law, and a progressive reduction in such price for each year during the

continued performance of such contract and also adequate assurance of

the continuing mutual performance of such contract according to the

conditions thereof, with proper indemnity to either party to such

contract against any possible violation, impairment, abrogation or

supersession thereof, within the term specified.