T-bill yields fell to their lowest level since last year. The Treasury sold $9 billion of 13-week bills at an average discount of 7.49 percent, down from 7.62 percent last week, and $9 billion of 26-week bills at an average discount of 7.40 percent, down from 7.52 percent last week. The investment rate was 7.74 percent on the three-month bills and 7.79 percent on the six-month bills. COMPANIES General Dynamics announced an executive reshuffling in a move to shore up its A-12 Navy attack plane program. Herbert F. Rogers, president and chief executive, will assume the duties of general manager of the Fort Worth division, and Vice Chairman William A. Anders will assume Rogers's corporate management responsibilities.

Eagle-Picher Industries filed a motion in federal court in New York seeking nationwide class-action status for all asbestos-related personal injury claims. Eagle-Picher has been handling asbestos litigation cases individually for several years.

Genetech asked the Food and Drug Administration to grant orphan drug status for Dnase for the treatment of patients with cystic fibrosis.

Nestle Enterprises put up for sale 65 restaurants operated by its Stouffer Restaurant subsidiary.

Resorts International said its bondholders have approved a reorganization plan designed to take entertainer Merv Griffin's casino company out of bankruptcy. The plan would give bondholders 78 percent of the company, dropping Griffin's ownership to 22 percent.

General Motors will reduce the work force at its North Tarrytown, N.Y., minivan plant by about 450 workers. REGULATION Renault Vehicules Industriels said the Justice Department's antitrust division has asked for more information and documents in connection with its tender offer for all the outstanding shares of Mack Trucks.

A GAO study faulted the Securities and Exchange Commission and the Commodity Futures Trading Commission for their conflicting analyses of last October's stock market slide.

Fourteen federal lawsuits against Perrier, triggered by the benzene contamination of some bottles of the mineral water, are being consolidated in Connecticut where the company's U.S. operation is based, officials said. ACQUISITIONS

Equifax said it has signed a definitive agreement to acquire Telecredit, a Los Angeles check and credit authorization company, for about $600 million.

Financier Mario Gabelli is part of a group that has acquired a 6 percent stake in Norfolk-based TVX Broadcast Group, which owns Washington television station WDCA (Channel 20).

Kansas City Power and Light made an $857 million tender offer for Kansas Gas and Electric, a move KCPL officials said would cut costs for both utilities and delay their need to add generating capacity. EARNINGS

RJR Nabisco Holdings said it lost $108 million in the second quarter compared with a loss of $319 million in the same quarter a year ago.

Time Warner recorded a net loss of $51 million compared with a loss of $102 million a year earlier.

Contel said second-quarter profit fell 36 percent.

Minnesota Mining and Manufacturing said profit rose 4.7 percent in the second quarter.

Manville said second-quarter earnings fell 24 percent.

Exxon said second-quarter earnings rose 11 percent.

Atlantic Richfield reported a 16 percent drop in second-quarter earnings.

Ashland Oil said profit for its fiscal third quarter rose 127 percent.

Union Carbide reported a 38 percent drop in second-quarter earnings.

Bankers Trust New York said second-quarter earnings were flat compared with a year ago. CONTRACTS

Fluor Daniel said it has won a $300 million contract for engineering, procurement and construction services on a 663-megawatt power plant in Hanover County, Va., that will be the largest independent power producer in the United States when completed in 1992. Power from the plant will be sold to Virginia Power.

Loral received a $71.5 million Air Force contract for development and operation of air crew training systems for MC-130 aircraft. INTERNATIONAL

A farm subsidy showdown between the United States and the European Community was postponed as world trade negotiators in Geneva expressed concern about a lack of progress in the GATT trade talks.

The British government said it might sell the state-owned electricity generator PowerGen to British conglomerate Hanson PLC rather than to the public.