While using the Keynesian model, describe the effect of a $40 billion increase in the money supply under these conditions: (a) a $40 billion increase in the money supply reduces the interest rate by 1 percent, (b) a 1 percent decrease in the interest rate increases investment spending by $60 billion, (c) the spending multiplier is 2.5, and (d) the economy is on the horizontal segment of its aggregate supply curve, so prices do not rise when aggregate demand increases.