Ford Motor Co., after selling its European brands, said it will discontinue its 71-year-old Mercury brand by the end of the year and expand its Lincoln lineup with a new small car. Ford’s board voted today to cease production of all four of Mercury’s models in the fourth quarter, Mark Fields, the automaker’s president of the Americas, told reporters. Ford will send letters to 1,712 Mercury dealers this week offering them buyouts and giving some the chance to merge the Lincoln half of their franchise with Ford showrooms, he said.