Talk that there will be more merger deals this year pushed stocks higher, with the office supply industry at center stage. On Monday, news reports said that OfficeMax (up 20.9 percent) and Office Depot (up 9.4 percent) are talking about combining. Staples Inc. rose 13.1 percent Tuesday as investors anticipated more mergers could be on the way. Analysts, though, caution that antitrust rules cloud the picture. Staples, for instance, tried to buy Office Depot in 1997 but was stopped by the Federal Trade Commission.