If Commercial Banks Hold Checkable Deposits of $100,000,reserves of $30,000,and

If commercial banks hold checkable deposits of $100,000,reserves of $30,000,and the required reserve ratio is 20 percent,what is the maximum additional amount by which the banking system can expand the money supply?

A) $20,000
B) $30,000
C) $50,000
D) $60,000
E) -$50,000