Answer:
$6.25 per ton of coal
Explanation:
the depletion base = purchase cost + restoration costs
depletion base = $26,000,000
depletion rate per ton of coal = (depletion base - salvage value) / estimated reserves = ($26,000,000 - $1,000,000) / 4,000,000 = $6.25 per ton of coal
The depletion rate follows the same concepts as depreciation of fixed assets, but instead of using a fixed asset, you are extracting materials and decreasing the value of the deposits.