A group including the New York investment...

A group including the New York investment firm of Warburg, Pincus & Co. said it has raised its stake in Mattel to 20.36%, up from about 18.3% last November. . . . Desert Partners Inc. of Midland, Tex., has extended its tender offer for Chicago-based USG Corp. to Thursday, according to a filing with the Securities and Exchange Commission . . . Louisiana-Pacific Corp.’s board gave final approval to the spin-off of Louisiana-Pacific’s Fibreboard Corp. subsidiary . . . The Federal Reserve said the average yield for one-year T-bills, the most popular index for making changes in adjustable rate mortgages rose to 7.40% last week from 7.33% the previous week . . . Baker Hughes Inc., Houston, reported that the number of working oil and gas rigs in the United States increased by nine this week to a total of 892. The rig count, the widely watched industry index of drilling activity, totaled 762 a year ago . . . Kleinwort Benson Ltd. said Fuji Bank Ltd. will acquire 24.9% of the share capital of Kleinwort Benson Government Securities Inc. of Chicago, which is Kleinwort Benson’s primary dealer in U.S. government securities . . . Emhart Corp. of Farmington, Conn., said it completed its previously announced purchase of Price Pfister Inc. for $18.50 a share, or about $215 million, to be part of Emhart’s consumer products business.