At a swap meet, there are 10 sellers who are each trying to sell a used 5.7L Chevy engine. Half the engines are in mint condition, with each valued by their sellers at $3,000. The other engines need repair, with each of these valued by their sellers at $1,000. Buyers value a mint engine at $3,500 and an engine that needs repair at $1,600. Sellers know whether their engine is in mint condition or needs repair, and buyers can distinguish between engines in mint condition and those needing repair. How many engines will be sold at the swap meet?