Ericsson Inc., a Richardson, Tex., telecommunications company, said it no longer will market personal computers in the United States . . . United Cable Television said it completed the previously reported acquisition of Times Mirror Cable Television's Hartford, Conn., system for $61.5 million . . . BankAmerica completed the $660-million sale of its San Francisco headquarters to real estate developer Walter Shorenstein . . . As part of a copyright settlement with Apple Computer, Digital Research said it will alter its GEM software programs and pay Apple an undisclosed amount . . . The proposed purchase of General Foods by Philip Morris for $5.63 billion was approved by both companies' directors . . . Zentec Corp., a Santa Clara, Calif., computer maker, has returned to a five-day workweek after having been on a four-day schedule since May; 30 workers were laid off.