On January 1, 2016, Skyward Company purchased a copy machine. The machine costs $320,000, its estimated useful life is 8 years, and its expected salvage value is $20,000. What is the depreciation expense for 2017 using double-declining-balance method?

Select one:

A. $80,000

B. $35,000

C. $52,500

D. $60,000

the answer is D but I don't know why it is answer and how can I solve a problem without a percentage?