Dee has been selling his corn crop to a local ethanol plant each fall. The ethanol plant and Dee do not have a written agreement. The ethanol plant always pays the current market price for the corn. Do Dee and the ethanol plant have a contract, and what type of contract is it: express or implied? Is it formal or informal? If the ethanol plant is taking all the corn Dee produces, is the contract a requirements contract? When will the contract come to an end?