Richard Roberts will be nominated by President Bush to fill a Democratic vacancy on the SEC created when Joseph Grundfest resigned in January to take a post at Stanford University. Richards is a partner in the law firm of Miller, Hamilton, Snider & Odom and had worked as an aide to Sen. Richard Shelby (D-Ala.).

Mortgage rates fell this week. Fixed-rate mortgages averaged 9.84 percent, down from 9.98 percent last week, while one-year adjustable-rate mortgages averaged 8.38 percent, down from 8.41 percent, the Federal Home Loan Mortgage Corp. said.

The Justice Department said it will file a civil antitrust suit to block Procter & Gamble's exclusive agreement to market and distribute Maalox, a product of Rhone Poulenc Rorer. P&G manufactures and markets Pepto-Bismol, and the agreement would "substantially lessen competition in the over-the-counter stomach remedies market in the United States," Justice said.

Ford Motor agreed to sell its Ford Aerospace subsidiary to defense electronics firm Loral Corp. for $715 million in cash. The transaction is subject to regulatory approval.

Montgomery Ward and Sears said they discussed and rejected "certain joint business opportunities." Spokesmen for both companies declined to comment on whether the retailers had considered merging.

Secretary of Education Lauro F. Cavazos said a deal will be ready within a few weeks to pay off the defaulted loans held by the Higher Education Assistance Foundation, one of the nation's insurers of student loans.

Campeau Corp. said Edward J. DeBartolo Corp.'s move to end its real estate partnership with Campeau may affect its efforts to sell shopping malls in New Jersey, Massachusetts and Washington state. Campeau is trying to sell its 50 percent stake in properties developed by the two companies, presumably to reduce its heavy debt load.

National Intergroup reported a first-quarter loss of $281.7 million, compared with a $12.9 million profit in the 1989 first quarter. Control over the company was wrested away from its chairman, Howard M. "Pete" Love, July 25 when Bethesda dealmaker Melvyn J. Estrin persuaded shareholders to oust Love and two allies from the board so that the company could be broken up and sold. Estrin's Centaur Partners Group said it was disappointed by the size of the write-offs taken by the board, but that its estimate of the inherent values of National's assets is not affected.

Domestic car sales slipped 0.6 percent in July from a year ago despite a 9.5 percent rise during the last 10 days of the month because of sharp gains by General Motors over relatively weak year-ago levels.