Gulf Consulting Co. reported the following on its December 31, 2013, balance sheet: Equipment (at cost).....$700,000 In a disclosure note, Gulf indicates that it uses straight-line depreciation over five years and estimates salvage value as 10% of cost. Gulf's equipment averages 3.5 years at December 31, 2013. What is the book value of Gulf's equipment at December 31, 2013?