No investment shall be made without the approval of the legislative authority of the city or town expressed by ordinance: PROVIDED, That except as otherwise provided by law, the legislative authority may by ordinance authorize a city official or a committee composed of several city officials to determine the amount of money available in each fund for investment purposes and make the investments authorized as indicated in RCW 35.39.030 as now or hereafter amended and the provisions of RCW 35.39.034, without the consent of the legislative authority for each investment. The responsible official or committee shall make a monthly report of all investment transactions to the city legislative authority. The legislative authority of a city or town or city official or committee authorized to invest city or town funds may at any time convert any of its investment securities, or any part thereof, into cash.