In the above figure, in order to achieve efficiency, a tax of ________ per unit is needed

If the government thinks the price that a consumer has to pay for a good is too high, then which of the following would solve this problem?

a. a price ceiling or an excise tax b. a price floor or an excise tax c. a price ceiling or a subsidy d. a price floor or a subsidy e. none of the above will lower the price a consumer has to pay for a good

What is the relevance of the marginal productivity principle in explaining the use of inputs in production?