First, check whether the stock constraint binds: ??? = ???(? , = ?- ??(? = 15 -? , =0 - ? =15 Since 15 > X- 12, this is sunicient evidence that the stock constraint does binc (ie. X : ?(+ ?, ). As a result, te total rent maxi.. .izing extraction pato will equate marginal net benefits of extraction in period 0 with the present value of marginal net benefits of extraction in period .' ???;? PV??? 1+? ??? = PL ??? 15- ? =15-? = 1.15 Since the constraint bin 's, 41 =X q. . Plug this identity into the MNB, = PVMNB, condition to obtain one equation in one unknown: 15-? 0 - 15 (12-? 0) =0 1.15 Solving this equation yields ?* = 6.63, so ?* = X - ? = 5.3