ECONOMY

T-bill yields increased. The Treasury auctioned 13-week bills at an average discount of 7.78 percent, up from 7.74 percent last week, and 26-week bills at an average discount of 7.67 percent, up from 7.64 percent.

COMPANIES

Dayton Hudson said about 850 employees working in Marshall Field's central organization will be dismissed in the next six months.

C. Itoh, a major Japanese trading company, will set up a joint venture with U.S. glassmaker PPG Industries to import and sell PPG's products in Japan.

Eastern plans to seek bankruptcy court permission to remove two unions from a committee of Eastern's creditors because it believes members of the Air Line Pilots Association and the International Association of Machinists have been giving travel agents confidential information from meetings in an effort to dissuade them from selling tickets on Eastern, sources said.

Michelin, the world's largest tire company, plans to cut 2,515 jobs from its French work force in an effort to hold down costs and meet foreign competition.

Tandy, the $4 billion electronics company, toughened its defenses against hostile takeover bids, reducing to 15 percent from 25 percent the ownership level that triggers a provision allowing shareholders to buy more common shares at a reduced price.

REGULATION

Maryland cannot force CBS to pay taxes on its national advertising revenue, after the state's Court of Appeals ruled that the state comptroller used the wrong method to try to collect taxes on such revenue. Before 1980, CBS, which owns a records sales office in Silver Spring and a toy manufacturing plant in Hagerstown, paid taxes based on sales, property and payroll in Maryland.

The Fed granted permission to Banca Commerciale Italiana to provide securities brokerage and foreign exchange services to institutional clients in the United States.

Ashland Oil was accused of fraud and attempting to obstruct justice in an amendment to an environmental lawsuit. The new charges contend Ashland made misleading statements about the toxicity of emissions from a refinery in Catlettsburg, Ky., and that it distributed things of value in the West Virginia county where the suit was initially filed.

CONTRACTS

MCI signed a four-year, $42 million contract to provide a private voice and data communications network to Ohio-based financial services firm Banc One. MCI also signed what it called a multimillion dollar communications contract with Household International, a financial services firm based in Chicago.

Compus Services Corp., a Rockville-based minority computer contractor, will provide systems integration services to Sears Business Systems Centers, the company's federal government marketing arm. Terms of the five-year contract were not disclosed.