Final answer:
In an open economy with high capital mobility and managed-floating exchange rates, fiscal policy may have a significant impact due to governmental spending and taxation, while heavy exchange rate intervention may render monetary policy less effective in directly influencing the exchange rate.
Step-by-step explanation:
In an open economy with high capital mobility, operating under a system of managed-floating exchange rates with heavy exchange rate intervention, the influence of fiscal and monetary policy on the economy can be complex. When it comes to fiscal policy, its impact can be significant due to the government's ability to influence demand through spending and taxation. However, monetary policy might be less effective in influencing the exchange rate directly due to heavy intervention by the government, although it can still indirectly influence the economy through targeting inflation and unemployment.
With a soft peg exchange rate, monetary policy often becomes entangled with exchange rates and international capital flows, as the central bank may need to decide whether to prioritize domestic goals or maintain the exchange rate peg. A floating exchange rate allows the central bank to focus more on domestic concerns such as inflation and unemployment, without the need to defend a specific exchange rate. However, a merged currency system would limit the independence of monetary policy, influencing both the exchange rate and domestic economic policies.
Considering all these aspects, option b. 'Fiscal policy has a significant impact, while monetary policy is ineffective in influencing the exchange rate' might be the closest to the expected scenario as fiscal policy could be seen exerting a clearer influence on the economy, while monetary policy effectiveness might be tempered by heavy interventions in the exchange rate.