Markets Start Week Lower on Failing Oil Prices and Twitter Set to Report

Wall Street started the week lower as traders digest earnings news and falling oil prices. If Goldman Sachs (GS) is right, it'll be good news at the pump for drivers. The firm now has the most bearish call on Wall Street for oil prices next year. The financial giant slashed its forecasts for crude oil to fall as low as $70 a barrel in the second quarter and Brent to fall as low as $80 a barrel. CVS (CVS) and Rite Aid (RAD) are blocking Apple Pay. The two drugstore chains disabled Apple's (AAPL) new mobile tool and are supporting a rival payment system. Before the bell, Merck (MRK) reported earnings of $0.90 a share. The drug maker narrowed its full-year earnings prediction. Investors will also look to Twitter (TWTR) as it reports after the close. Shyam Patil, analyst at Wedbush Securities says aside from the earnings 'another key growth is user growth and engagement' for the social micro-blogging site.