The figure depicts a supply-of-loanable-funds curve and two demand-for-loanable-funds curves. A graph of r versus Q shows a straight line, D 1, decreasing linearly from left to right, a second straight line, D 2, decreasing linearly from left to right above and parallel to D 1, and a third straight line, Supply, increasing linearly from left to right. Refer to Figure 26-2. What is measured along the horizontal axis of the graph? a. The quantity of loanable funds b. Private saving c. The interest rate d. The size of the government budget deficit or surplus