Within 10 days after the hearing on assessment is completed, duplicate copies of each of the following shall be signed by the president and secretary and attached to the last volume of each part of the assessment book:
(a) The statement of the assessor showing the total valuation of the land assessed.
(b) The order of the board of supervisors fixing the rate of assessment on the land.
(c) The annual estimate of the board of directors. Thereupon the assessment is completed.