True or false? If false, explain why. a. The total public debt is more relevant to an economy than the public debt as a percentage of GDP. b. An internally held public debt is like a debt of the left hand owed to the right hand. c. The Federal Reserve and Federal government agencies hold more than three-fourths of the public debt. d. The portion of the U.S. debt held by the public (and not by government entities) was larger as a percentage of GDP in 2007 than it was in 1995. e. In recent years, Social Security payments to retirees have exceeded Social Security tax revenues from workers and their employers.