Include correctly labeled diagrams, if useful or required, in explaining your answers. A correctly labeled diagram must have all axes and curves clearly labeled and must show directional changes. If the question prompts you to "Calculate," you must show how you arrived at your final answer.

The banking system in Country A has limited reserves, and the central bank of Country A has become concerned about a steep decline in investment spending.

(a) Identify an open market operation that Country A's central bank is likely to implement to address the decline in investment spending.

(b) Draw a correctly labeled graph of the money market and show the effect of the central bank's policy identified in part (a) on the nominal interest rate.

(c) Explain the effect of the change in the nominal interest rate shown in part (b) on aggregate demand in the short run.

(d) If the banking system in Country A instead had ample reserves rather than limited reserves, identify a policy action the central bank is likely to implement to address the decline in investment spending.