DE10-13 Chevron, the giant oil company, holds huge reserves of oil and gas assets. At the end of 20X0, Chevron's cost of mineral assets totaled approximately $18 billion, representing 2.4 billion barrels of oil and gas reserves in the ground. 1. Which depreciation method do Chevron and other oil companies use to compute their annual depletion expense for the minerals removed from the ground? 2. Suppose Chevron removed 0.6 billion barrels of oil during 20X1. Record Chevron's depletion expense for 20X1. 3. At December 31, 20X0, Chevron's Accumulated Depletion account stood at $11.5 billion. If Chevron did not add any new oil and gas reserves during 20X1, what would be the book value of the company's oil and gas reserves after recording depletion at December 31, 20X1?