On July 1, 2010, Low Enterprises sold equipment with an original cost of $85,000 for $40,000. The equipment was purchased January 1, 2009, and was depreciated using the straight-line method assuming a five year useful life and $5,000 salvage value. The necessary entries for 2010 include a:

(correct answer is Debit to Depreciation Expense for $8,000 but I don't know how)