Use the figure below to answer the following questions. Interest rate (percent per year) Interest rate (percent per year) MS MS MD MD 0 Real money (billions of 2007 dollars) (a) (b) Interest rate (percent per year) MSO MS MD MDo MD Real money (billions of 2007 dollars) Interest rate (percent per year) MS, MSO MD Real money (billions of 2007 dollars) 0 Real money (billions of 2007 dollars) (c) (d) Figure 8.5.1 Refer to Figure 8.5.1. Everything else remaining the same, which graph best shows the effect of an increase in real GDP?