On January 1, 2015. Bithe Smarey & Co purchased 535,500 worth of office equipment with an estimated useful life of seven years and an estimated residual value of $4.000 Bthe Smarey uses the straight-line method of amortization for all office equipment. At the beginning of 2018. Bthe Smamey revised its estimate of the useful life of the office equipment to a total of nine years. The 2018 amortization penses O A 53,000 OB. 53.667 OG $2.000 OD 52.444