Acme Builders is considering merging with Joes Construction to achieve economies of scope sufficient to drive the combined firms costs down by at least $500,000. Acme Builders has costs of $5,000,000 on sales of $8,000,000, and Joes Construction has costs of 3,000,000 and sales of $5,000,000. What would be the minimum combined average cost of sales expressed as a percentage necessary to achieve the cost reduction goal?