3. On January 1, 2015, Petersen Enterprises purchased natural resources for $1,800,000. The company expects the resources to produce 12,000,000 units of product. (1) What is the depletion cost per unit? (2) If the company mined and sold 20,000 units in January, what is depletion expense for the month? 4. On January 2, 2015, Olathe Company purchased a patent for $240,000. The patent has an 8-year estimated useful life and a legal life of 20 years. Instructions Prepare the journal entry to record patent amortization.