Jackson Corporation Acquired Equipment on January 1, 2010, for $320,000

Jackson Corporation acquired equipment on January 1, 2010, for $320,000. The equipment had an estimated useful life of 10 years and an estimated salvage value of $25,000. On January 1, 2013, Jackson Corporation revised the total useful life of the equipment to 6 years and the estimated salvage value to be $20,000. Using the straight-line method of depreciation, what is the book value as of December 31, 2013?

A) $146,000
B) $154,333
C) $159,000
D) $161,000