Williams Corporation purchased a depreciable asset for $400,000 on January 1, 2010. The estimated salvage value is $40,000, and the estimated useful life is 9 years. The straight-line method is used for depreciation. In 2013, Williams on charged its estimates to a total useful life of 5 years with a salvage value of $60,000. What is 2013 depreciation expense? a)$40,000 b)$60,000 c)$110,000 d)$120,000