BDM International Inc. has won a $16 million, five-year contract to develop a new computer system for Montana's Department of Social and Rehabilitation Services.

Officials said the computer system, known as the Economic Assistance Management System, will be the largest automated system in the Montana state government. It will be used to more accurately administer and process applications for aid to families with dependent children, food stamps and Medicaid.

BDM, which plans to work with Anderson Consulting of Chicago, will design and develop the system in the first two years, then maintain the system in the remaining years of the contract.

BDM has undertaken a similar project in New Mexico, where the McLean company developed a system for that state's social services and medical assistance programs.

BDM International is a subsidiary of Ford Aerospace Corp.

Ethyl Corp. announced plans to buy assets and inventories of a Quantum Chemical Corp. plant in Texas for about $48 million.

Under the deal announced last week, Richmond-based Ethyl will take over Quantum's polyalphaolefin production center in Houston. The chemical is used to provide fluidity and stability in motor oil, increasing fuel efficiency.

The plant, which can produce nearly 30 million gallons annually, will be Ethyl's first such venture. The deal is subject to regulatory review.

Host International of Washington, a division of Marriott Corp., received a long-term contract from the City of Cleveland to operate the merchandise concessions at Cleveland's Hopkins International Airport.

Host, which will spend more than $2 million to renovate the airport's concourse when construction begins in early fall, said the contract represents more than $60 million in estimated revenue.

American Mobile Satellite Corp. of Washington and Telesat Mobile Inc. of Ontario, Canada, reached agreement to provide facilities and core services for mobile satellite services in the United States and Canada and to provide backup capacity in the event of a satellite or launch failure. The agreement includes priority aeronautical operations traffic, airline passenger communications, and radio, data and mobile telephone services.

Airline Economics Inc. of Washington won a contract from Host International of Washington to provide consulting services over the next three years for undisclosed terms.

Smith-Sternau Organization Inc. of Washington, which designs and markets association-sponsored insurance programs, changed its name to Seabury & Smith Inc.

Contel ASC of Rockville received a contract for a national video teleconferencing network from O/E Learning Inc. of Troy, Mich. Terms were not disclosed.

History Associates Inc. of Rockville was awarded a contract by the National Archives Trust Fund Board of Washington to help prepare an exhibit for the archives' commemoration of the 50th anniversary of World War II.

Manning, Selvage & Lee Inc. of Washington opened a joint-venture public relations firm with Tokyu Agency International and Kyodo Public Relations, both of Japan. The new firm, Tokyu MS&L Inc., is based in Tokyo.

Cor/Net Inc. of Rockville sold a minority stock interest to the Woodbridge Co. Ltd. of Toronto.

Edelman Public Relations Worldwide of Washington won a contract from the Palm Oil Promotion Council of Malaysia to develop a public relations and educational program.

Marketing General Inc. of Alexandria received a contract to manage the membership list of the American College of Health Care Administrators and introduced the Plastic Engineers and Professional Action Deck, a list of plastics industry technical professionals.

Data Sciences Inc. of Silver Spring received a contract from 11 newspapers nationwide to install its UNIX-based Papertrak hardware and software system.

Information Systems Marketing of Washington won a contract from the international division of Group Hospitalization and Medical Services Inc. of Washington to design and implement a videotext system to handle health insurance eligibility questions for its clients traveling out of the country.

Penril Corp. of Gaithersburg repurchased $2.6 million of its outstanding increasing rate senior unsecured notes. The company made $325,000 in the transaction and reduced its total debt to $6.4 million.

Timothy J. Gorman opened the Gorman Group Inc., a marketing and public relations company, in Washington.

3D/Environmental Inc. of Houston formed 3D/Environmental Services Inc., an applied environmental services company based in Alexandria.

Chotin Group Corp. of Denver, which specializes in structured finance and asset securitization, opened an office in Washington.

Jefferson Bank and Trust Co. of Greenbelt opened an office in Rockville.

Gyrus Systems Inc. of Midlothian, Va., introduced Advanced Transcript, a Microsoft Windows-based training and education administrative software system.

Eckard Group Inc. of Bethesda formed Infoscan, a subsidiary that provides optical mark scanning services and products.

Announcements of news and developments affecting Washington area companies should be sent to Regional Report, Business News Department, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071.