Sec. 6. (a) The incidental, inspection, and engineering costs that are authorized by the preliminary resolution and included in the estimate may be added to the cost of an improvement and included in the assessment roll in the aggregate amount to be apportioned and assessed against the benefited property.
(b) The amount of incidental, inspection, and engineering costs included in the assessment roll may not exceed the amount of the incidental, inspection, and engineering costs included in the estimate.