Suppose that, in the Mundell-Fleming model, the equilibrium exchange rate is above the level e' at which the central bank wishes to keep the currency. Suppose that the central bank takes steps to peg the exchange rate to e'. The domestic money supply expands, and the exchange rate falls. But the full set of conditions belongs in a 18x course 4. Suppose exchange rates are flexible.
Output falls a lot.
It would be very effective. Expansionary fiscal policy is very effective at boosting output in a small open economy with fixed exchange rates. It would be ineffective. Attempts to expand the money supply in a small open economy immediately leak out into the wider world under fixed exchange rates.