All used cars are lemons or peaches. Owners know whether or not their car is a lemon, but buyers do not; that is, the quality of a car is private information. There are many more buyers than sellers. Buyers value a peach at $4,000 and a lemon at $200; owners value a peach at $3,000 and a lemon at $100. Owners can have their cars inspected for $100. If they do have their car inspected, they will receive a certificate that shows whether the car is a lemon or a peach. Show that owners of peaches will have their cars inspected and will sell those cars for $4,000. Show also that the owners of lemons will not obtain a certificate and will sell their cars for $200.