An expansionary monetary policy is likely to increase aggregate demand in the short run and may possibly increase aggregate supply as well. Therefore, an expansionary policy would increase GDP.
If the government adopts an expansionary monetary policy, more money will exist in the economy. An important consequence of this is that interest rates will drop and consumers and businesses will have an easier time borrowing money. When this happens, AD will rise as customers buy more goods on credit. AS may rise if businesses can use the borrowed money to increase capacity quickly. If either of these things happens, GDP will increase.