If within 30 days after receipt of such notice the owner shall propose voluntarily to sell and transfer such property to the agency upon terms and conditions to be mutually agreed upon between the owner and the agency and approved by the Alabama Public Service Commission, and serve a copy of such proposal upon the agency and upon the commission, the commission shall fix a time and place to hear and consider such proposal and notify all parties interested therein. If the terms and conditions of purchase and sale shall be agreed upon by and between the owner and the agency and approved by the commission, the commission shall announce its approval thereof by appropriate order, and the agency shall by resolution or ordinance, as the case may be, authorize and direct the execution on the part of the agency of such contract in writing and other instrument and take any and every other action with reference thereto necessary or appropriate to consummate such purchase and sale and the transfer to the agency of possession of such acquired property and payment therefor in accordance with the terms of such agreement. If the owner fails or refuses to advise such agency within 30 days after receipt of such notice of its purpose to sell such property, then the agency may proceed as provided by law to construct, condemn or otherwise acquire a plant or system within the designated territory; and the advice to be given by the owner to such agency shall be sufficient if it advises that the owner is willing to sell the property provided the valuation as finally determined by the commission or court is satisfactory to the owner. Upon the owner advising of its willingness to sell such property, acquisition of the property sought to be acquired shall proceed with the rights and privileges to the respective parties as set forth in this division.