Equipment was acquired on January 1, 2006, at a cost of $90,000. The equipment was originally estimated to have a residual value of $5,000 and an estimated life of 10 years. Amortization has been recorded through December 31, 2007, using the straight-line method. On January 1, 2008, the estimated residual value was revised to $6,000 and the useful life was revised to a total of 8 years. Determine the amortization expense for 2008