At the time and place so fixed or at any time or place to which the hearing is continued, the board shall hold the hearing provided for by the resolution at which hearing any person interested, including all persons owning land in the district or improvement district to which the hearing pertains, may appear and be heard concerning any matters set forth in the resolution or any matters material thereto. At the conclusion of the hearing on the proposed plan, or the proposed changes or supplements, the board may, by resolution, adopt the proposed plan of works, or amend the plan of works previously adopted in accordance with the proposed changes or supplements. The board shall set forth the estimated cost of carrying out any plan of works and the purpose to be accomplished. If there is any change in the estimate of cost of carrying out the plan of works and the purpose is to be accomplished, the amended total of the estimated expense shall be set forth specifically.