I can't figure out Double-Declining-Balance Method

Comparing Three Depreciation Methods Dexter Industries purchased packaging equipment on January 8 for $530,200. The equipment was expected to have a useful life of four years, or 6,400 operating hours, and a residual value of $43,800. The equipment was used for 2,240 hours during Year 1, 1,344 hours in Year 2, 1,792 hours in Year 3, and 1,024 hours in Year 4. Required: 1. Determine the amount of depreciation expense for the four years ending December 31 by (a) the straight-line method, (b) the units-of-activity method, and (c) the double-declining-balance method. Also determine the total depreciation expense for the four years by each method. Round the answer for each year to the nearest whole dollar