Early in the year, Amazon purchased River mine for $30,000,000. The mine was estimated to contain 400,000 tons of ore and to have a residual value of $7,500,000 after mining operations are done. During that year, 115,000 tons of ore were removed. At the year-end, the book value of the mine is which of the following?
a. 22,500,000
b. 6,468,750
c. 23,532,250 or
d. 30,000,000