IN REAL LIFE, there are three factors that will determine your earning power throughout your working life (purchasing power). - (1) demand for what you do, (2) quality and skill with which you do what you do, and (3) the ease or difficulty of your being replaced for what you do. How do you think that these factors would apply to an entire open macro economy? Do you think that these three factors have anything to do with the economy-wide trade balance or with the nominal value of its currency