On May 1, 2018, Ziggy Inc. purchased a piece of machinery for one of its factories. Ziggy paid $800,000 for the equipment, which has an expected useful life of 10 years. The machine's salvage value is estimated to be $80,000. If Ziggy uses the straight-line method of depreciation, what is the book value of the machine on December 31, 2019? $680,000 $576,000 $600,000 $656,000