In a closed economy, saving and investment must be equal, but this is not the case in an open economy. In the following problem, you will explore how saving and investment are connected to the international flow of capital and goods in an economy. Before delving into the relationship between these various components of an economy, you will be asked to recall some relationships between aggregate variables that will be useful in your analysis. Recall the components that make up GDP. National income ( YY ) equals total expenditure on the economy's output of goods and services. Thus, where CC = consumption, II = investment, GG = government purchases, XX = exports, MM = imports, and NXNX = net exports: