A coal mining company has owned a mine for the past five years. During this time the following tonnage of ore has been removed each year: $25,000$; $32,000$; $36,000$; $30,000$; and $28,000$ tons. The mine is estimated to contain a total of $500,000$ tons of coal. The initial cost of the mine is P$12,000,000.$ If the company had a gross income for this coal of P$220$ per ton for the first two years, and P$300$ per ton focal of last three the larger determine the depletion charge for the year using the larger values for the two methods, and $($b$)$ compute the percent of the initial cost that has been written off in the five years.