Q. Explain why under fixed exchange rate, monetary policy is ineffective whereas under floating exchange rate it is effective in rising output.

Answer:  In floating by purchasing domestic assets the central bank cause an initial excess supply of domestic money that concurrently pushed the domestic interest rate downward and weakens the currency.  Though under fixed exchange rate the central bank will oppose any tendency of the currency to depreciate by selling foreign assets for domestic money and consequently removing the initial excess supply of money its policy move has caused.