Only one commercial bank in the banking system has an excess reserve, and its excess reserve is $400,000. This bank makes a new loan of $300,000 and keeps an excess reserve of $100,000. If the required reserve ratio for all banks is 12.5 percent, the potential expansion of the money supply from this new loan is

money supply will increase by 2,400,000

Explanation:

the expansion f the money supply will be:

the money multiplier will be:

1/reserve ratio = 1/0.125 = 8

300,000 x 8 = 2,400,000

The reasoning for the multiplier effect is the following:

once the money is received, it will be used, and the person who receive the cash will deposit their proceeds.

This amount, can generate a new loan for, the remainder after subtracting the required reserve.

300,000 - 12.5% = 262,500

And this, once used will also end in a deposit. This opens the posibility for another loan, after reducing the reserve

262,500 - 12.5% = 229,687.5‬

This can be reapeat again and again and the limit for this is the formula state above:

multiplier effect = 1/reserve ratio