I am confused on these questions. What are equations I could use and how can I use them properly

Straight-Line Depreciation A refrigerator used by a wholesale warehouse has a cost of $98,050, an estimated residual value of $6,800, and an estimated useful life of 10 years. What is the amount of the annual depreciation computed by the straight-line method? 95:] Depreciation by Units-of-activity Method A dieselpowered tractor with a cost of $259,440 and an estimated residual value of $3,800 is expected to have a useful operating life of 83,000 hours. During April, the tractor was Operated 200 hours. Determine the depreciation for the month. If required, carry out any division to two decimal places. $:]