Final answer:
To target a 4% interest rate, the central bank must adjust the money supply according to the basic quantity equation of money, with a constant nominal income of 500. Contractionary policies can reduce the money supply, while an example increase of $100 billion in supply would expand nominal GDP by $300 billion, assuming a constant money velocity of 3.
Step-by-step explanation:
If the central bank wants to adjust the interest rate to 4%, it needs to consider the basic quantity equation of money, which states that the money supply multiplied by the velocity is equal to the nominal GDP (money supply × velocity = nominal GDP). Keeping the nominal income (Y) constant at 500, the central bank can leverage this equation to calculate the new money supply necessary to target the desired 4% interest rate.
To determine the change in quantities of money and central bank money when keeping the interest rate at 4%, one must consider that the central bank's actions would reflect a contractionary monetary policy if they intend to raise the interest rate. This type of policy typically reduces the money supply and consequently the quantity of central bank money. Additionally, factors such as deposit insurance, the economic cycle, and changes in the discount rate may affect these quantities.
Using the information provided about an increase of $100 billion in money supply with a velocity of 3, the nominal GDP would expand by $300 billion ($100 billion × 3). This provides an idea of how changes in the money supply can significantly influence the nominal GDP, given the velocity of money as a constant factor.