Final answer:
The increase in the money supply with an increase in bank reserves of $50 and a reserve ratio of 0.1 is $500. The money multiplier is calculated as 10, using the formula 1 divided by the reserve ratio. Option A is correct.
Step-by-step explanation:
To calculate the increase in the money supply associated with an increase in bank reserves of $50, we must first determine the money multiplier.
The money multiplier formula is 1 divided by the reserve ratio. In this case, the desired reserve-deposit ratio is 0.1 (which is the same as the reserve ratio), hence the money multiplier will be 1/0.1 = 10.
Now, we multiply the increase in bank reserves ($50) by the money multiplier (10) to get the increase in the money supply. So, the increase in the money supply would be $50 * 10 = $500.
For the multiple-choice question about the general rule for calculating the money multiplier, the correct answer is A. 1/desired reserve as it represents the reciprocal of the desired reserve ratio.