Arrange the following steps in the correct order to understand the impact of per-unit taxes on market efficiency: A) Government imposes a per-unit tax on producers, B) Producers increase their marginal costs, C) Producers reduce output to align with socially efficient levels, D) Market equilibrium is adjusted to reflect the new costs.

To understand how per-unit taxes affect market efficiency, we start with the government imposing a tax on producers. This tax increases the marginal costs for producers, meaning it costs them more to make each unit of their product. As a result, producers will reduce their output because they need to adjust to these higher costs and align their production with what is socially efficient. Finally, the market equilibrium changes to reflect these new costs, leading to a new balance between supply and demand. For example, if a tax is placed on a soft drink, producers might make fewer drinks because the tax raises their costs, which ultimately affects how much consumers buy.