The Units-Of-Production Method Is Commonly Used to Calculate the Amount

The units-of-production method is commonly used to calculate the amount of depreciation and amortisation expense to be written-off each year from the accumulated costs of exploration and development of a mining venture.Which of the following formulae best expresses the calculation of the amortisation rate under this method?

A)
$$\begin{array}{l}\begin{array} { c } \text { Accumulated } \\\text { Cost }\end{array} + \begin{array} { c } \text { Estimated } \\\text { Future Costs }\end{array} - \begin{array} { c } \text { Estimated } \\\text { Residual Value }\end{array}\\\hline\text { Economically Recoverable Reserves }\end{array}$$
B)
$$\begin{array}{l}\begin{array} { c } \text { Accumulated } \\\text { Cost }\end{array} + \begin{array} { c } \text { Estimated } \\\text { Future Costs }\end{array} - \begin{array} { c } \text { Estimated } \\\text { Residual Value }\end{array}\\\hline\text { Economically Market Value of the Venture }\end{array}$$
C)
$$\begin{array}{l}\begin{array} { c } \text { Accumulated } \\\text { Cost }\end{array} + \begin{array} { c } \text { Estimated } \\\text { Future Costs }\end{array} - \begin{array} { c } \text { Estimated } \\\text { Residual Value }\end{array}\\\hline\text { Present Value of Estimated Future Net Revenue }\end{array}$$
D)
$$\begin{array}{l}\begin{array} { c } \text { Accumulated } \\\text { Cost }\end{array} + \begin{array} { c } \text { Estimated } \\\text { Future Costs }\end{array} - \begin{array} { c } \text { Estimated } \\\text { Residual Value }\end{array}\\\hline\text { Estimated Future Net Revenue }\end{array}$$