When the prices are at a certain level, the central bank increases the money supply, causing the interest rate to fall in the money market. The decline in interest rates increases planned investment expenditures and therefore aggregate expenditures. The increase in money supply is the increase in production at a certain price level. In this case, the AD curve will shift to the right. Assume that the aggregate supply curve is constant, the aggregate demand curve shifs to the right from AD1 to AD2. In this case, the equilibrium shifts from point D1 to point D2. Eventually, the general price level in the economy increases from P1 to P2, while the equilibrium income level increases from Y1 to Y2.