Luray Company Purchased a New $40,000 Truck on January 1

Luray Company purchased a new $40,000 truck on January 1, 2012. The truck was expected to last 4 years and have no salvage value. During 2013, Loray's depreciation expense on the truck was $12,000. Which of the following depreciation methods is Loray Company using to depreciate the truck?

A) Sum-of-the-years'-digits
B) Double-declining-balance
C) 150-percent-declining balance
D) Straight-line