In graphical representation, how is the aggregate demand function obtained?

Option 1 -> In graphical representation, functions plotted against the same x-axis (income/output) are added vertically to show total demand at each income level.

Option 2 -> Horizontal addition is used when combining different market demand curves or when variables are on different axes, not for aggregate demand components.

Option 3 -> Subtracting consumption from investment would give a negative value and doesn't represent aggregate demand.

Option 4 -> Multiplying functions is not used for aggregate demand; AD is the sum of components, not their product.

Hence, Option 1: By adding the consumption and investment functions vertically -> In a graph with Income/Output on the x-axis and Expenditure on the y-axis, the aggregate demand (AD = C + I) is obtained by vertically adding consumption and investment at each income level. For example, if at income level Y₁, consumption is 100 and investment is 50, the aggregate demand at that point would be 150 on the y-axis. This vertical summation creates the aggregate demand curve, which lies above both individual curves -> correct