4. Amplify Petroleum holds huge reserves of oil. Assume that at the end of 2017, Amplify Petroleum's cost of oil reserves totaled $80,000,000, representing 100,000,000 barrels of oil. Suppose Amplify Petroleum removed and sold 20,000,000 barrels of oil during 2018. Joumalize depletion expense for 2018 . (Assume no residual value. Record debits first, then credits. Select the explanation on the last line of the journal entry table.)