The extension agent shall submit monthly an accurate itemized account of all expenditures incurred by the agent in the regular conduct of duties to the North Dakota state university extension service for examination and audit. When charges are made by an extension agent for money expended in the performance of official duties and consistent with the approved budget, expenditures must be covered by a subvoucher or receipt according to county policy for reimbursement. The subvoucher or receipt must show at what place, on what date, and for what the money expended was paid. The extension agent shall forward the subvouchers or receipts with the bill, claim, account, or demand against the county. Charges made for transportation expenses may not exceed the amounts provided by section 11-10-15, and must be in itemized form showing the mileage traveled, the days when and how traveled, and the purpose of travel, verified by affidavit. The account must be transmitted and recommended for payment by the North Dakota state university extension service which shall audit and approve or disallow any expense item.