According to the quantity theory of money, if the gross domestic product is $6 trillion and M1 money supply is $ 800 billion, the velocity of the M1 money supply is:（）

单项选择题The Laffer curve begins at:（）

A. zero tax revenues and ends at zero tax revenues.
B. zero tax revenues and ends at maximum theoretical tax revenues.
C. minimum tax revenues and ends at maximum theoretical tax revenues.

单项选择题If the central bank unexpectedly shifts to a more restrictive monetary policy, the most likely effect（）

A. an increase in real interest rates.
B. a decrease in real interest rates
C. an increase in asset prices.