Figure 34-4 The graph of Interest Rate versus M shows a straight line, M D 1, decreasing linearly, a second straight line, M D 2, decreasing linearly to the left and parallel to M D 1, and a vertical line, M S, extending from the horizontal axis. r sub 1, r sub 2, and r sub 3 are marked on the vertical axis, from highest to lowest. A horizontal line extends from r sub 1 and passes through a point on M D 2 and touches the intersection of M D 1 and M S. A horizontal line extends from r sub 3 and touches the intersection of M D 2 and M S, below the intersection of M D 1 and M S. A horizontal line extends from r sub 2 and passes through M D 1, passes through M S between the intersections of M D 1 and M S, and M D 2 and M S, and touches a point on M D 1. Refer to Figure 34-4 . Which of the following events could explain a decrease in the equilibrium interest rate from r 1 to r 3 ? a. An increase in the price level