US stocks opened muted on Friday as a holiday-shortened week and downbeat month drew to a close and as the Chicago Mercantile Exchange resumed trading following a data center glitch. The tech-heavy Nasdaq Composite (^IXIC) led stocks lightly upward on Black Friday, gaining around 0.4% in the first minutes of trading. The generalist S&P 500 (^GSPC) and Dow Jones Industrial Average (^DJI) both rose by a bit more than 0.2%. The CME Group restored operations after a long outage disrupted live trading in futu ...