§ 2.1. When any city of the first class, having authority so to do, shall borrow money and issue bonds or other securities therefor, except in the case of the giving of notes for temporary loans as may be authorized by law and except in the case of the issuance of bonds or other securities under the act of October 18, 1972 (P.L. 955, No. 234), known as “The First Class City Revenue Bond Act,”¹ the authorities thereof may sell the same at, above or below their par value plus accrued interest either at a private negotiated sale or a public sale to the highest responsible bidder, as shall be determined by the authorities of such city, after public notice by advertisement of either the official invitation for bids or of the availability of the official invitation for bids in at least one newspaper of general circulation published in such city at least one time not less than ten (10) days nor more than thirty (30) days prior to the date fixed for opening bids. Before the authorities of such city shall make any private sale of bonds or securities, the legislative body of such city shall adopt by a vote of a majority of the members thereof a resolution finding that a private sale is in the best financial interest of the city. This section shall apply to all borrowings and the issuance of bonds or other securities therefor, whether heretofore or hereafter authorized.