Stocks moved lower after a choppy morning of trading as global growth worries weighed on investor confidence. The IMF reiterated its forecast for weak global growth and cut its forecasts for the U.S., the world's largest economy. Apple  (AAPL - Get Report) led the Dow Jones Industrial Average after launching its Apple Pay service in Russia. The payment system is now available in 10 countries since first launching in 2014. Pandora  (P) spiked after Goldman Sachs added it to its conviction buy list and suggested a 34% upside to its current trading price. The firm pointed to opportunities in on-demand and premium subscriptions. Salesforce.com (CRM - Get Report) has agreed to acquire marketing and advertising startup Krux. The cloud-computing company agreed to a cash-and-stock deal worth around $700 million.