(2) The offer shall be in writing and shall, upon being submitted to the board, be irrevocable until such time as the board, under ORS 547.655 to 547.695, has a reasonable opportunity to issue, sell and deliver such refunding bonds to replace and discharge the outstanding indebtedness on acceptance of the offer; provided, that the offer shall not be revoked while any suit, action or proceeding involving the issuance, sale or delivery of such refunding bonds is in process of determination nor until a reasonable time after the final determination of such suit, action or proceeding.
(3) When authorized by a majority vote of the electors of the district, the exchange may be made on a basis of less than par for the refunding bonds, in which event the board of supervisors shall, in its resolution declaring its intention to sell the refunding bonds, also require the secretary of the board to give notice of the proposed sale by publication thereof for four consecutive weeks in three newspapers within the state, one of which shall be in the county in which the district is situated.