Investors breathed a sigh of relief on March 11 as the benchmark indices closed flat amid increased uncertainty and heightened volatility. The 30-share Sensex closed flat at 74,102.32. Levels down by 12.85 points or 0.02 per cent. The Nifty 50 index closed flat with a positive bias at 22,497.9 levels up by 37.6 points or 0.17 per cent.