In January, 2020, Sheffield Corporation purchased a mineral mine for $5400000 with removable ore estimated by geological surveys at 1800000 tons. The property has an estimated value of $300000 after the ore has been extracted. The company incurred $1600000 of development costs preparing the mine for production. During 2020, 590000 tons were removed and 540000 tons were sold. What is the amount of depletion for 2020? (when recording depletion, when do we use 590k tons and when do we use the 540k)