redevelopment agency to do so, it shall be liable to such agency in the penal sum of twice the amount of the cost of the work, which sum may be recovered in a civil action; (d) that any municipality may contract to retain or accept, close, relocate, construct, reconstruct and maintain specified streets, playgrounds, parks or other public facilities within the area of the proposed redevelopment. Upon consummation of the contract for sale, lease or other transfer of a site to a redeveloper, any municipality may provide for the extension of such streets, sidewalks and public utilities as are necessary to its use for residential, commercial or public purposes.