“Cost” as applied to production includes the cost of raw materials, labor and all overhead expenses of the producer.

“Cost” as applied to distribution means the invoice or replacement cost, whichever is lower, of the article or product to the distributor and vendor, plus the cost of doing business by the distributor and vendor and in the absence of proof of cost of doing business a markup of 6 percent on such invoice or replacement cost shall be prima facie proof of such cost of doing business.

“Cost” as applied to warranty service agreements includes the cost of parts, transporting the

parts, labor, and all overhead expenses of the service agency.

Discounts granted for cash payments shall not be used to reduce costs.