According to the quantity theory of money equation, when velocity is stable, which of the following best describes the effects of an increase in the money supply?

Group of answer choices

An increase in the money supply causes a proportional increase in nominal GDP but not in the price level.

An increase in the money supply causes a proportional increase in the price level and real GDP.

An increase in the money supply causes a proportional increase in the price level and nominal GDP.

An increase in the money supply causes a proportional increase in the real GDP but not in the price level.