The income and expenditure approaches to measuring a nation's GDP can be combined using the circular flow model. Categorize each of the following flows as part of either aggregate demand or national income. While national income and domestic product must be equal, income must also equal expenditure for each of the six sectors in the circular flow diagram: firms, consumers, governments, financial system, investors, and the "rest of the world," For example, the amount of flowing into the financial system sector must equal the amount of - flowing out of this sector