Oppenheimer & Co.’s Jessica Reif lowered her rating on News Corp., parent of Fox Inc. and 20th Century Fox Studio, from a buy to “market performer.”She said it’s still a positive issue, based on News Corp.’s long-term outlook. The company’s stock closed off 5/8 to 41 1/8, near its 52-week high. Stanton R. Cook will retire Jan. 1 as chairman of Tribune Co.’s board of directors. Charles T. Brumback was elected to replace Cook and will continue as president/CEO. Cook will remain on board and continue as chair of Tribune’s Chicago Cubs baseball team. Tribune owns seven television stations and publishes seven daily newspapers, including the Chicago Tribune.