Answer: $390 per ton
Step-by-step explanation:
The depletion per ton is:
= Total cost of acquiring the coal mine / Number of tons that can be extracted
= (Acquisition cost + intangible development cost + Fair value of restoration) / Number of tons that can be extracted
= (1,800,000 + 360,000 + 180,000) / 6,000
= $390 per ton