At an initial point on the aggregate demand curve, the price level is 125, and real GDP

Question:

At an initial point on the aggregate demand curve, the price level is 125, and real GDP is $15 trillion. When the price level falls to a value of 120, total autonomous expenditures increase by $250 billion. The marginal propensity to consume is 0.75. What is the level of real GDP at the new point on the aggregate demand curve?