ECONOMY T-bill yields fell. The Treasury auctioned 52-week bills at an average yield of 6.81 percent, the lowest since 6.74 percent May 5, 1988. The investment rate was 7.28 percent. Money-market fund assets fell by $1.23 billion to $417.1 billion in the latest reporting week, the Investment Company Institute said.

COMPANIES AT&T agreed to explore construction of a new fiber optic cable across the Atlantic with a German state telecommuni- cations agency. To be completed by early 1993, it would be able to carry about 100,000 simultaneous telephone calls. Advanced Micro Devices, a California-based manufacturer of electronic equipment, reeling from a $17.8 million loss in the third quarter, is laying off about 200 employees to cut costs. Banner Industries shareholders approved the company's name change to Fairchild Corp. The aerospace company also formally announced the move of its headquarters from Cleveland to Chantilly, currently the operations center of its Fairchild Industries subsidiary. Newsweek and U.S. News and World Report announced that advertising rates will rise in 1991 for the weekly news magazines. The increases, which follow a similar move at rival Time, were blamed on rising costs for postage and news coverage.

INTERNATIONAL Mexico received three bids for the state-controlled telephone company, the deadline for private companies interested in buying part of Telefonos de Mexico. The government kept the amounts of the bids secret.

ACQUISITIONS Canadian Pacific Hotels acquired MetHotels of Phoenix from Metropolitan Life Insurance. Terms were not disclosed.

REGULATION The Department of Transportation gave final approval to United Airlines's planned new routes between Chicago and Tokyo.

COURTS Sharon Steel may be near initiating a $300 million reorganization plan. A trustee for the bankrupt steelmaker and several of the company's major creditors have reached agreements.

EARNINGS Volvo reported a loss of $35 million for the first three quarters of 1990, compared with a profit of $1.1 billion in the year-ago period. The Gap reported a 39 percent increase in third-quarter profit. Honda said its second-quarter earnings were up 25.6 percent.

ODD LOTS Mobil said three of its chemical engineers -- William F. Briggs, 52; Paul S. Vaughan, 38; and Karel M. Forman, 32 -- all residents of upstate New York, were among those killed in the crash of Alitalia Airlines Flight 404 near Zurich Wednesday. Iroquois gas pipeline opponents say they will appeal a federal agency's decision to approve the 370-mile pipeline, which will bring Canadian natural gas to utilities and gas companies in New England, New York and New Jersey.