Answer:
purchase cost January 1, 2017 = $35,000,000
useful life 20 years, salvage value $5,000,000
depreciation expense per year
straight line method = ($35,000,000 - $5,000,000) / 20 = $1,500,000 per year
accumulated depreciation = $4,500,000
book value on December 31, 2019 = $35,000,000 - ($1,500,000 x 3) = $30,500,000
double-declining-balance method:
depreciation expense year 1 = 2 x 1/20 x $35,000,000 = $3,500,000
depreciation expense year 2 = 2 x 1/20 x $31,500,000 = $3,150,000
depreciation expense year 3 = 2 x 1/20 x $28,350,000 = $2,835,000
accumulated depreciation = $9,485,000
book value on December 31, 2019 = $35,000,000 - $9,485,000 = $25,515,000