Wall St set to open higher for first time in three days

Wall Street was set to open higher for the first time in three days on Tuesday as investors await Federal Reserve Chair Janet Yellen's speech this week for clues on the next interest rate hike. As the U.S. earnings season winds down, the focus shifts to the annual meet of global central bankers at Jackson Hole, Wyoming, from Thursday, for clues on the health of the global economy and Yellen's stand on raising rates. Yellen is scheduled to speak on Friday and will use the opportunity to either su