We cap off a volatile week with policy talk from Fed Chair Yellen and some key earnings on Friday, March 27th. Investors will be at the ready to pick apart clues from Yellen's speech on monetary policy at a San Francisco Fed conference Friday afternoon. On the data front, we'll get the third and final estimate of fourth-quarter GDP in the morning. Economists expect the measure to tick up to 2.4% growth over the quarter. BlackBerry will give its quarterly performance before the bell Friday. Analysts expect net losses halved from a year earlier, though sales are expected to fall nearly 20%.