As you did not provide options here I managed to find your question and the answer would be that the prices can be easily set by the government is definitely not an advantage of a price-based system.
There are two ways the prices are set in the economic system:
1. They can be set by the government or
2. They can be freely set by the laws of supply and demand.
This would be correct for a short time in the war. Then out of popular demand and a decision to keep foreign powers from intervening, the focus of the war was abolition of slavery.
Mercantilism was an economic theory whereby colonies were founded and maintained for the benefit of the mother country. Furthermore, the government had the ability to regulate its own economy with the intent of dominating over rival countries. Mercantilist countries tended to favor the creation of domestic (national) industries and businesses, and tried to discourage importing goods from other economies (usually by tariffs.) Effective mercantilism was thought to enable a country to become economically self-sufficient. This is the sort of relationship England had with the American colonies. Mercantilism dominated the economic landscape. Colonists were only able to trade with British merchants, and colonial manufacturing ventures were largely frowned upon. The British Navigation Acts regulated these policies. Smuggling was common. Politically, the British practiced a policy of salutary neglect.