U.S. stocks tried to break their losing streak, starting mildly higher at Friday's opening bell. Investors will be listening closely as Federal Reserve Chair Janet Yellen speaks at a Fed conference in San Francisco. Her speech starts at 3:45 pm, eastern. The U.S. economy slowed in the fourth quarter as previously estimated. The third estimate of GDP expanded at 2.2%, unrevised from last month’s forecast. BlackBerry (BBRY) is starting the day sharply higher after reporting a surprise profit in the fourth quarter. Wall Street was expecting a loss from the smartphone maker. BlackBerry’s revenue did continue to slide, down 30% from year ago. Google (GOOG) will pay its new Chief Financial Officer more than $70 million over the next two years. The pay package includes salary, restricted stock and bonuses. Ruth Porat joins the tech giant from Morgan Stanley (MS).