Assume that the following balance sheet portrays the state of the banking system. The banks currently have no excess reserves.

Assets Liabilities and Net Worth
(Billions of Dollars)
Total reserves 5 Checkable Deposits 50
Loan 25
Securities 20
Total 50 Total 50

What is the required reserve ratio?
a. 5%
b. 40%
c. 10%
d. 25%