On January 1, 2017, Wasson Company purchased a delivery vehicle costing $40,000. The vehicle has an estimated 3-year life and a $4,000 residual value. Wasson estimates that the vehicle will be driven 72,000 miles. What is the vehicle's depreciation expense for the year ended December 31, 2019 assuming Wasson uses the units-of-production depreciation method and the vehicle was driven 35,000 miles during 2017, 25,000 miles during 2018 and 14,000 miles in 2019?

$7,000

$12,000

$7,778

$6,667

None of the above