4. A coal mine purchased 3 years ago for SAR 30 million was estimated to contain 3,500,000 tons of coal. During the past 3 years the amount of coal removed was 20,000, 19,000, and 21,000 tons, respectively. The gross income obtained in these 3 years was SAR 960,000 for the first year, SAR 1,200,000 for the second year, and SAR 1,300,000 for the third year. Determine (a) the cost depletion allowance for each year and (b) the percentage of the purchase price depleted thus far