Tennecott Mining Company purchased a tract of land with estimated copper ore deposits totaling 800,000 tons. The purchase price for the land was $2.2 million. During the first year of operation, Tennecott mined and sold 90,000 tons of ore. During the second year, Tennecott mined and sold 120,000 tons of ore. At the beginning of the third year, new geological engineering estimates determined that a total of 440,000 tons of copper ore remained. During Year 3, 140,000 tons of ore were mined and sold.

1. What was the original depletion rate used by Tennecott in Years 1 and 2?

2. Make the accounting entries for depletion expense for Tennecott Mining Company at the end of Years 1 and 2.

3. What is the depletion rate for Year 3, and what accounting entry should be made to reflect the change in accounting estimate in Year 3?