On December 1, Carla Vista Electronics has three DVD players left in stock. All are identical, all are priced to sell at $65. One of the three DVD players left in stock, with serial #1012, was purchased on June 1 at a cost of $40. Another, with serial #1045, was purchased on November 1 for $37. The last player, serial #1056, was purchased on November 30 for $31.