ECONOMY Five-year Treasury note yields fell in yesterday's auction to the lowest level in a year. The average yield was 7.95 percent, down from 8.57 percent on Aug. 29. After-tax corporate profits increased 6.7 percent from July through September, an increase that some analysts attributed primarily to inflation.

COMPANIES A Bell Atlantic unit and American Management Systems, both of Arlington, will jointly market software for telecommunications billing and customer information to international clients. Fiat, the Italian auto giant that temporarily laid off 70,000 workers earlier this month to cut production, said it will spend $4.5 billion to build two new production plants by 1994. McDonnell Douglas said it would be able to adhere to a $6.57 billion ceiling in developing and producing the first six C-17 cargo jets. The Los Angeles Times had reported that an internal Air Force study had estimated McDonnell Douglas would spend $7.1 billion to finish the jets. Merrill Lynch froze hiring and executive pay raises and warned its workers against spending on perks such as club dues in an attempt to cut costs. The firm also banned merit pay increases in 1991. Merrill already has laid off about 3,000 employees this year. Norfolk Southern said it will shuffle four top officers in Norfolk and will offer early retirement to 250 lower-level managers who work in Roanoke, Atlanta and other outposts and are 55 and older with five or more years with the company. Prodigy has issued stricter guidelines for sending private messages that a group of dissidents claim are aimed at quelling their protests over charges for electronic mail on the national online service. Subaru of America will trim its work force by as much as 10 percent to cut costs. USX Chairman Charles A. Corry expressed reluctance to meet with a committee formed by Carl Icahn to press the financier's case that the company should separate its steel and energy businesses.

ACQUISITIONS Manufacturers Hanover said it agreed to purchase $1.6 million in deposits at 13 New York City-area branches of Goldome FSB. It said 10 of the Goldome branches will be converted into Manufacturers offices and three will be closed.

REGULATION A law banning cigarette vending machines in all public places except for taverns and hotel bars was adopted by the New York City Council and Mayor David Dinkins. The law, intended to take cigarettes out of the hands of minors, orders the machines removed by Jan. 31, 1992. It is similar to measures already in effect in Minneapolis and Salt Lake City and being considered in Washington. The Commerce Department accused selected Japanese and Singaporean manufacturers of personal word processors of "dumping" -- selling their products below cost -- in the United States. Chile should be placed back on the list of developing countries that are eligible to export products to the United States on a duty-free basis, U.S. Trade Representative Carla Hills said. Chile's preferred trade status was suspended in 1988 after a U.S. finding that Chile had restricted workers' rights.

PEOPLE Marianne K. Smythe has been named to head the Security and Exchange Commission's investment management unit. Giancarlo Parretti, the Italian financier who is chairman of MGM-Pathe Communications Co., submitted a bid for MCA Inc. on Monday only hours after the company agreed to be acquired by Matsushita Electric. "Off the record," said one Wall Street analyst, "the Street thinks it's a joke." ODD LOTS The union for Baltimore dockworkers rejected management's final contract offer, increasing the chance of a strike and causing one shipping line to announce plans to begin diverting cargo from the Port of Baltimore. AT&T carried a record 148.4 million long-distance calls on Monday, breaking the record set the day after last year's San Francisco earthquake.