Stocks were moderately higher Monday with biotech stocks leading the way. The Nasdaq and the Dow Jones industrial average rose 0.4% and the S&P 500 gained 0.5%, closing above the 2000 level for the first time. After the close, Amazon (AMZN) announced it was paying $970 million to buy Twitch, a live video platform for gamers. Viewers can watch other people play video games.