The gradual decrease in the value of natural resource is called depletion. The deplection expense is calculated on the cost net off salvage value.
[tex] Depletion expense per ton of ore=\frac{(Cost of resource - salvage value)}{Expected Mine} =\frac{(1544800-252000)}{2,020,000} =$0.64 [/tex]
Therefore, Depletion expense per ton of ore would be $0.64 per ton of ore.