4. In the textbook and in class, we examined a variety of non-renewable resource models that featured stable demand over time, constant marginal extraction cost, a fixed and known stock of the resource, a renewable backstop technology, and competitive outcomes. Efficient extraction of the resource under these conditions requires that rent rise at the rate of interest. a. What is rent? b. Why must rent rise at the rate of interest? c. If rent rises at the rate of interest, and marginal extraction cost is constant, explain what happens to the real price of the resource over time. d. How would you describe the behavior of real resource prices over time that is reflected in empirical data on prices? How does this compare to the behavior of prices implied by the model? e. Explain what changes in the model specification described in this question (#3) might account for the actual behavior of real resource prices over time