Arco put half its Lyondell Petrochemical subsidiary...

Arco put half its Lyondell Petrochemical subsidiary up for sale to the public in an initial stock offering of 40 million shares which, at $30 a share or $1.2 billion, is the third biggest by a U.S. company . . . Smith Barney, Harris Upham & Co. said it is reentering risk arbitrage trading, which it suspended in early 1988 . . . Sacramento-based System Integrators Inc. said it agreed to pay $250,000 to settle four class-action suits relating to the firm’s management buyout . . . The Food and Drug Administration approved Warner-Lambert’s drug Lopid for use in reducing the risk of heart disease, a move that analysts predict will boost the company’s 1989 profit.