The First Welfare Theorem states that O a. competitive markets are efficient when there are no externalities and no concentration of market power. O b. competitive markets are efficient even in the presence of externalities. O c. taxes and regulations always lower a society's welfare, on the aggregate. O d. substantial inequality is a necessary by-product of an economy that operates efficiently. QUESTION 5 The Principle of Comparative Advantage says that O a. two countries can benefit from trade, but only when one country has a higher productivity (i.e., output per worker) for one group of products while the other country has a higher productivity for another group of products O b. two countries can benefit from trade, even when one country has a higher productivity (i.e., output per worker) for all products than the other country. What matters are differences in relative productivity between the different products. O c. the more productive country benefits more from trade than the less productive country. QUESTION 6 Which of the following is among the purposes of an Integrated Assessment Model? O a. Estimation of the "Social Cost of Carbon," which is the cost (present and future) of a unit of carbon emissions. O b. Merge models of economic growth with climate and carbon-cycle models. O c. Neither of the above answers is correct. O d. Both of the above answers are correct