Archie runs a small mineral exploration business (as a sole proprietorship). In 2019, he purchased land (for $68,000) where he suspected a magnesium deposit was located. He incurred $18,000 of exploration costs related to the development of the magnesium mine in 2019 and an additional $22,000 of exploration costs in 2020. Archie elected to deduct these expenditures for regular tax purposes in both 2019 and 2020.

In 2021, given a decline in magnesium prices, Archie chose to sell the property for $66,000 rather than bring the mine to production.

What AMT adjustments are required in 2021 related to mine exploration expenditures and the sale of the land?