Fees and charges for inspection and certification services shall comprise the cost of salaries, travel, per diem, and related expenses to cover the costs of performing the service. Fees shall be for actual time required to render the service calculated to the nearest 30-minute period. The hourly rate shall be $47.40. The overtime rate for service performed outside the inspector's regularly scheduled tour of duty shall be $53.70. The rate of $64.45 shall be charged for work performed on Sundays and holidays.