To achieve the social optimum, the government could set a tax equal to per unit sold.

To achieve the social optimum, the government could set a tax equal to $6 per unit sold.

Explanation:

The social optimum seems to be the distribution chosen by a good social planner who is limited by resources allocation only. In particular, the social optimum can not be achieved if there are limitations on the social planner's policy tools.

Proponents of significant increases or cuts in the United States marginal tax rates have long provided statistical evidence of the existence of their proposals.

The elasticity of earned income figures was actually a relatively new description of behavioral reactions to marginal taxes that have historically been studied.

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