How do I solve this depreciation question?

Depreciation by units-of-activity Method Prior to adjustment at the end of the year, the balance in Trucks is $407,300 and the balance in Accumulated DepreciationTrucks is $124,860. Details of the subsidiary ledger are as follows: Accumulated Miles Estimated Estimated Depreciation Operated Truck Residual Useful at Beginning During No. Cost Value Life of Year Year 1 $81,500 $12,225 200,000 miles 30,000 miles 2 116,300 13,955 410,000 $23,260 41,000 3 99,500 13,930 214,000 $79,600 21,400 4 110,000 13,200 320,000 $22,000 38,400 a. Determine for each truck the depreciation rate per mile and the amount to be credited to the accumulated depreciation section of each subsidiary account for the miles operated during the current year. Keep in mind that the depreciation taken cannot reduce the book value of the truck below its residual value. Round the rate per mile to two decimal places. Enter all values as positive amounts. Credit to Rate per Mile Miles Accumulated Truck No. (in cents) Operated Depreciation 4 E 33,400 #:1 To... 1-: b. Journalize the entry to record depreciation for the year. v ' :1