Nola Mining Company purchased a tract of land containing ore for \(\$ 630,000\). After spending \(\$ 90,000\) in exploration costs, the company determined that 600,000 tons of ore existed on the tract but only 500,000 tons could be economically removed. No other costs were incurred. When the company finishes with the tract, it estimates the land will be worth \(\$ 180,000\). Determine the depletion cost per ton.