. Derive the AD curve

The Aggregate Demand (AD) curve is a representation of the total demand for goods and services in an economy at different price levels. It is derived from the IS-LM model, which is a macroeconomic model that describes the interaction of demand (IS curve) and supply (LM curve) in the goods and money markets.

Here are the steps to derive the AD curve:

1. Identify the IS-LM Model: The IS-LM model is a macroeconomic model that describes the interaction of demand (IS curve) and supply (LM curve) in the goods and money markets. The IS curve represents all combinations of interest rates and output at which the goods market is in equilibrium, while the LM curve represents all combinations of interest rates and output at which the money market is in equilibrium.

2. Find the Equilibrium Point: The equilibrium point in the IS-LM model is where the IS curve and the LM curve intersect. This point represents the level of output and the interest rate at which both the goods and money markets are in equilibrium.

3. Change in Price Level: Now, suppose the general price level in the economy changes. This will shift the LM curve because a change in the price level affects the real money supply, which in turn affects the interest rate and the level of output.

4. Shift of LM Curve and New Equilibrium: If the price level rises, the real money supply decreases, shifting the LM curve upwards (or to the left). This leads to a higher interest rate and lower level of output. Conversely, if the price level falls, the real money supply increases, shifting the LM curve downwards (or to the right). This leads to a lower interest rate and higher level of output.

5. Plot the AD Curve: The AD curve is derived by plotting the level of output at the new equilibrium points against the corresponding price levels. The AD curve is downward sloping, indicating that as the price level falls (rises), the level of output rises (falls).

In summary, the AD curve is derived from the IS-LM model by considering how changes in the price level affect the equilibrium level of output. The AD curve shows the inverse relationship between the price level and the level of output in the economy.