Stocks posted restrained gains Monday, as volume cooled off. The Nasdaq tacked on 0.3%, while the S&P 500 and the Dow Jones industrial average stepped up 0.4% and 0.8%, respectively. Volume ran about 11% to 15% lower than Friday’s pace, according to preliminary calculations. Blue chip United Technologies (UTX) led the Dow with a 2% gain as it bounced off its 50-day moving average line. Volume was average.