4. Critical Accounting Estimates and Judgments Goodwill Impairment Testing Estimated Recoverable Reserves and Resources Decommissioning and Restoration Provisions In preparing these consolidated financial statements, we make estimates and judgments that affect the amounts  recorded. Actual results could differ from our estimates. Our estimates and judgments are based on historical experience  and other factors we consider to be reasonable, including expectations of future events. The estimates and assumptions  that could result in a material effect in the next financial year on the carrying amounts of assets and liabilities are  outlined below. Goodwill impairment testing is based on discounted cash flow models prepared by internal experts with assistance  from third-party advisors when required. Note 15 outlines the significant judgments and assumptions made in  performing goodwill impairment testing. The assumptions used are based on management’s best estimates and are  reviewed by senior management. Changes in these assumptions may alter the results of goodwill impairment testing,  impairment charges recorded in the statement of income and the resulting carrying values of assets. Mineral reserve and resource estimates are based on various assumptions relating to operating matters. These include  production costs, mining and processing recoveries, cut-off grades, long-term commodity prices and, in some cases,  exchange rates, inflation rates and capital costs. Cost estimates are based on feasibility study estimates or operating  history. Estimates are prepared by appropriately qualified persons, but will be affected by forecasted commodity prices,  inflation rates, exchange rates, capital and production costs and recoveries amongst other factors. Estimated recoverable  reserves and resources are used to determine the depreciation of property, plant and equipment at operating mine  sites, in accounting for deferred stripping costs, in performing impairment testing and in forecasting the timing of the  payment of decommissioning and restoration costs. Therefore, changes in the assumptions used could affect the  carrying value of assets, depreciation and impairment charges recorded in the income statement and the carrying value  of the decommissioning and restoration provision. The decommissioning and restoration provision is based on future cost estimates using information available at the  balance sheet date. The decommissioning and restoration provision is adjusted at each reporting period for changes  to factors such as the expected amount of cash flows required to discharge the liability, the timing of such cash  flows and the discount rate. The decommissioning and restoration provision requires other significant estimates and  assumptions including the requirements of the relevant legal and regulatory framework and the timing, extent and  costs of required decommissioning and restoration activities. To the extent the actual costs differ from these estimates,  adjustments will be recorded and the income statement may be affected (Note 20). Generations 93