Rates for the sale of any material or supplies which have been administered, purchased, maintained, or manufactured with ER&R funds for the use of the county road department must include, but are not limited to, the following:

(1) Cost of purchasing, storing, and distributing the material or supplies;

(2) Direct and indirect cost of maintaining and operating facilities specific for ER&R material and supplies;

(3) ER&R program administration.

ER&R rates for material and supplies shall be determined by the county engineer or other appointee of the county legislative body. However, if the rates are set by an appointee other than the county engineer, the county engineer shall review the proposed rates and certify to the legislative body that the proposed rates are an appropriate use of county road funds as required by RCW 36.80.030.