Please provide full explanations and solutions, not only letter asnwers, thank you.

There are 30 units of a nonrenewable resource (we have perfect information and know that these are of uniform quality) available, which can be mined and sold during two periods (0 & 1). The inverse demand function (Marginal Benefit function) for the resource can be represented by P =400-10.Q. The cost of mining Q units in any time period is C(Q)=100 .Q, implying the marginal cost of mining is C'(Q) =MC(Q) =100 3. If the extraction (mining) firm follows the optimal (surplus-maximizing) extraction path, and if the operative interest rate is 25% (0.25), how much of the resource will be extracted during the first period (period 0)? A. No more than 12 units. B. More than 12 units but not more than 14 units. C. More than 14 units but not more than 16 units. D. More than 16 units but not more than 18 units. E. More than 18 units. 4. If the extraction firm follows the optimal (surplus-maximizing) extraction path, and if the operative interest rate is 25% (0.25), what is the Marginal Net Benefit (MNB) in the first period (period 0) (this is also called Hotelling Rent or Scarcity Rent)? A. $0 - MNBo