During 2014, Corporation acquired a mineral mine for $4,000,000 of which $400,000 was ascribed to land value after the mineral has been removed. Geological surveys have indicated that 10 million units of the mineral could be extracted. During 2014, 1,800,000 units were extracted and 1,500,000 units were sold. What is the amount of depletion expensed for 2014?

A) 360,000

B) 400,000

C) 468,000

D) 540,000