In January 2020, Brilliant Industries purchased the Topaz Mine at a cost of $10,000,000. The mine is estimated to contain 500,000 carats of stone and to have a residual value of $500,000 after mining operations are completed. During 2015, 50,000 carats of stone were removed from the mine and sold. In this situation: a) The amount of depletion charged to expenses from during 2020 is? b) The Net Book Value of the mine at the end of 2020 is? c) The inventory value of the extracted carats of stone