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Shares of Groupon jumped after Deutsche Bank AG analysts upgraded the stock, citing optimism that increasing use of its mobile app can boost sales. Groupon, which started out promoting discounts via e-mail alerts, is adding customers as more smartphone users turn to its mobile app, said analyst Ross Sandler. Revenue will surge 53 percent to $3.56 billion in 2015 over last year, he estimated. Analysts’ on average projected 2015 sales of $3.04 billion, Bloomberg reported.