On January 1, 2019, Rio Co. purchased a machine for $39,980, and expects to use the machine a total of 32,000 hours over the next four years. Rio Co. set the salvage value on the machine at $3,500, and used the machine 6,000 hours in 2019 and 7,200 hours in 2020.

What is the amortization expense for 2020 if Rio Co. uses the double-declining balance amortization method?

A) $8,208

B) $9,995

C) $18,240

D) $9,120

Please tell me how to solve above question. Thank you.