A park and recreation service area may reimburse the county for any charge incurred by the county current expense fund which is properly an expense of the service area, including reasonable administrative costs incurred by the offices of county treasurer and the county auditor in providing accounting, clerical or other services for the benefit of the service area. The county legislative authority may, where a county purchasing department has been established, provide for the purchase of all supplies and equipment for a park and recreation service area through the department. The park and recreation service area may contract with the county to administer purchasing.