ASC 740 provides a more-likely-than-not standard in evaluating whether a valuation allowance is necessary after weighing all of the available evidence. When evaluating the need for a valuation allowance, we consider all available positive and negative evidence, including the following: • the status of our operations in the particular taxing jurisdiction, including whether we have commenced production from a commercial discovery; • whether a commercial discovery has resulted in significant proved reserves that have been independently verified; • the amounts and history of taxable income or losses in a particular jurisdiction; • projections of future income, including the sensitivity of such projections to changes in production volumes and prices; • the existence, or lack thereof, of statutory limitations on the period that net operating losses may be carried forward in a jurisdiction; and • the creation and timing of future income associated with the reversal of deferred tax liabilities in excess of deferred tax assets. Derivative Instruments and Hedging Activities. We utilize oil derivative contracts to mitigate our exposure to commodity price risk associated with our anticipated future oil production. These derivative contracts consist of collars, put options, call options and swaps. We also use interest rate derivative contracts to mitigate our exposure to interest rate fluctuations related to our long-term debt. Our derivative financial instruments are recorded on the balance sheet as either assets or a liabilities measured at fair value. We do not apply hedge accounting to our oil derivative contracts. Effective June 1, 2010, we discontinued hedge accounting on our interest rate swap contracts and accordingly the changes in the fair value of the instruments are recognized in earnings in the period of change. The effective portions of the discontinued hedges as of May 31, 2010, were included in accumulated other comprehensive income or loss (‘‘AOCI’’) in the equity section of the accompanying consolidated balance sheets, and were transferred to earnings when the hedged transactions settled. Estimates of Proved Oil and Natural Gas Reserves. Reserve quantities and the related estimates of future net cash flows affect our periodic calculations of depletion and assessment of impairment of our oil and natural gas properties. Proved oil and natural gas reserves are the estimated quantities of crude oil, natural gas and natural gas liquids which geological and engineering data demonstrate with reasonable certainty to be recoverable in future periods from known reservoirs under existing economic and operating conditions. As additional proved reserves are discovered, reserve quantities and future cash flows will be estimated by independent petroleum consultants and prepared in accordance with guidelines established by the SEC and the FASB. The accuracy of these reserve estimates is a function of: • the engineering and geological interpretation of available data; • estimates of the amount and timing of future operating cost, production taxes, development cost and workover cost; • the accuracy of various mandated economic assumptions; and • the judgments of the persons preparing the estimates. Asset Retirement Obligations. We account for asset retirement obligations as required by the ASC 410—Asset Retirement and Environmental Obligations. Under these standards, the fair value of a liability for an asset retirement obligation is recognized in the period in which it is incurred if a reasonable estimate of fair value can be made. If a reasonable estimate of fair value cannot be made in the period the asset retirement obligation is incurred, the liability is recognized when a reasonable 99