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

D)
$$\frac { \begin{array} { c } \text { Accumulated } \\\text { Cost }\end{array} + \begin{array} { c } \text { Estimated } \\\text { Future Costs }\end{array} - \begin{array} { c } \text { Estimated } \\\text { Residual Value }\end{array} } { \text { Estimated Future Net Revenue } }$$