On April 1, 2019, Leon Company purchased a copper mine at a cost of $84,000,000. The mine was estimated to contain 4,000,000 tons of ore and to have a residual value of $24,000,000 after mining operations are completed. During the year, 750,000 tons of ore were removed from the mine. On December 31, 2019, the book value of the mine is: Select one: A. $90,000,000 B. $52,500,000 C. $72,750,000 D. $48,750,000