(Telecompaper) Facebook reported fourth-quarter revenues up 52 percent year-on-year to USD 5.84 billion, led by continued strong growth in mobile advertising. Mobile accounted for 80 percent of ad revenue in the quarter, up from 69 percent a year earlier. The company generated a net profit of USD 2.27 billion or USD 0.79 per share, up from USD 1.52 billion or USD 0.54 per share a year earlier. After free cash flow of USD 2.14 billion in the quarter, Facebook ended 2015 with USD 18.43 billion in total cash.