On December $1,$ Windsor, Inc. has three DVD players left in stock. All are identical, all are priced to sell at $$87.$ One of the three DVD players left in stock, with serial #$1012,$ was purchased on June $1$ at a cost of $$53.$ Another, with serial #$1045,$ was purchased on November $1$ for $$48.$ The last player, serial #$1056,$ was purchased on November $30$ for $$39.$