a. Graphically illustrate how, in a two period model of a nonrenewable resource, economic efficiency in the presence of a positive rate of discount implies increased consumption (and lower prices) today, than would be observed with a discount rate of zero. (7 points) b. What are some of the factors that could make social user costs different from private user costs in the case of mineral extraction? (6 points) c. Graphically illustrate how user cost is affected by the expectation that future demand for a resource will shift outward on today’s efficient rate of extraction.