When calculating depletion, what is the proper treatment of residual value?
A) There is no residual value in the calculation of depletion expense.
B) The residual value is subtracted from cost to determine the depletable base.
C) The residual value is added to cost to determine the depletable base.
D) Residual value is ignored until the end of the asset's life at which time it is used to limit the final year's expense amount.