Explain calculations

Year 1 January 8. Purchased a used delivery truck for $61,440, paying cash. March 7. Paid garage $140 for changing the oil, replacing the oil filter, and tuning the engine on the delivery truck. December 31. Recorded depreciation on the truck for the fiscal year. The estimated useful life of the truck is 8 years, with a residual value of $12,900 for the truck. Year 2 January 9 . Purchased a new truck for $70,560, paying cash. February 28. Paid garage $330 to tune the engine and make other minor repairs on the used truck. April 30. Sold the used truck for $40,440. (Record depreciation to date in Year 2 for the truck.) December 31. Record depreciation for the new truck. It has an estimated residual value of $12,700 and an estimated life of 7 years. Year 3 September 1. Purchased a new truck for $84,000, paying cash. September 4. Sold the truck purchased January 9, Year 2, for $42,900. (Record depreciation to date for Year 3 for the truck.) December 31. Recorded depreciation on the remaining truck. It has an estimated residual value of $15,100 and an estimated useful life of 10 years. September 4 Depreciation September 4 Sale