If the board finds that it would be for the best interests of the district and the proposed improvement district to form the improvement district, it shall make and enter in its minutes a final order:
(a) Approving the petition.
(b) Forming the improvement district.
(c) Levying the assessment if any is provided for and if the assessment is necessary.
(d) Apportioning the assessment, if levied, to the land in the improvement district according to benefits.