Final answer:
Selling $40 million in government securities to commercial banks when the reserve ratio is 20 percent will reduce the excess reserves by $8 million.
Step-by-step explanation:
When the Federal Reserve Banks sell $40 million in government securities to commercial banks and the reserve ratio is 20 percent, the effect will be to reduce the excess reserves by $8 million. This is because the banks are required to hold a certain percentage of their deposits as reserves, and selling the securities would decrease their excess reserves by the corresponding amount. It does not directly affect the money supply.