How does amortization of drilling costs differ under the three methods? Include in your answer a discussion of the method used, which reserves are used, if any, and which drilling costs are amortized—dry versus successful, exploratory well versus development well, completed versus uncompleted, and IDC versus L&WE. Also include the cost center used—i.e., are drilling costs amortized separately or by some grouping? Assume for full cost all possible costs are amortized.