On January 1, 2011, Graham Corporation acquired machinery at a cost of $600,000. Graham adopted the double-declining balance method of depreciation for this machinery and had been recording depreciation over an estimated useful life of 10 years, with no residual value. At the beginning of 2013, a decision was made to change to the straight-line method of depreciation for the machinery. The depreciation expense for 2013 should be:
a) $76,800
b) $60,000
c) $48,000
d) $26,743