On January 1, 2020, Boom Electrical purchased equipment for $40,000. Residual value at the end of an estimated four-year service life is expected to be $4,000. The company expects the machine to operate for 20,000 hours. Calculate depreciation expense for 2020 using units-of-production using machine hours. The machine operated for 8,000 hours in 2020. The depreciation expense is:

A. $9,000

B. $16,000

C. $14,400

D. none of the answers above are correct