If the costs of an improvement determined and assessed under section 40-23-07 or 40-23.1-04 exceed the costs of the work as contained in the engineer’s estimate under section 40-22-10 by seventy percent or more, the governing body of the city shall secure an audit of all costs included in the assessment for the project, prepared in accordance with generally accepted auditing standards. The audit report must include a separate statement of the engineer’s estimate of the cost of the work, the actual cost of the work, the cost of extra work, engineering fees, fiscal agent’s fees, attorney’s fees, publication costs, warrant printing costs, interest costs, and each separate item of expense incurred in making the improvement and levying the assessment for the improvement. The city shall make a copy of the audit report available without charge to any person who requests a copy. The audit report is not required if the costs of an improvement exceed the costs of the work as contained in the engineer’s estimate by seventy percent or more because of a petition to enlarge the district under section 40-22-09 or a request for additional work within the district by the owners of a majority of the area of the property in the district. Audit and copying expenses under this section must be paid by the city and may not be paid from special assessment funds.