According to Ian Redpath and Brian O'Sullivan, which of the following is correct regarding the depreciation element of the standard mileage rate? A. It cannot be used to decrease basis upon sale or trade-in of the vehicle. B. It must be used to decrease basis upon sale or trade-in of the vehicle. C. It may be used to increase basis upon sale or trade-in of the vehicle. D. It must be used to increase basis upon sale or trade-in of the vehicle.