Pepco Holdings (POM) and Exelon (EXC) have asked D.C. regulators to reconsider a rejection of their proposed $6.8 billion merger. The electric companies argued that the merger would stabilize rates and improve service. Stocks were modestly higher after a massive slump a day earlier. The health care sector was the best performer as bruised and battered biotech stocks clawed back some of the gains suffered over the past week. Consumer confidence unexpectedly rose in September to its highest level since January. Lower gasoline prices and a healthy jobs environment helped to offset worries over extreme market volatility this month. Business research firm IHS (IHS) moved higher after beating quarterly estimates on its top- and bottom-line.