Which of the following statements is incorrect? a. Property, plant and equipment (PP&E) assets are reported at their net book value. b. Impairment of PP&E assets is determined by comparing the asset's net book value to the sum of the asset's expected future cash flows. c. Accumulated depreciation is the sum of all depreciation expense that has been recorded to date and is reported as a contra asset account. d. Gains on asset sales are defined as Net Book Value of Asset Sold is greater than Proceeds from Sale.