On April 17, 2021, the Loadstone Mining Company purchased the rights to a coal mine. The purchase price plus additional costs necessary to prepare the mine for extraction of the coal totaled $3,840,000. The company expects to extract 960,000 tons of coal during a four-year period. During 2021, 320,000 tons were extracted and sold immediately.

Required:
a. Calculate depletion for 2021.
b. Is depletion considered part of the product cost and included in the cost of inventory?