Straight line Depreciation = (Original Value -
Salvage Value) / Useful Life
= ($800000 - 80000) / 4 = $180000
For 2020 = $180000 x 9/12 = $135000
Double Declining Balance Depreciation =
Beginning Book Value x 2 times Straight line rate
For 2020 = $800000 x 50% x 9/12 = $300000
For 2021 = ($800000 - 300000) x 50% = $250000
Sum of Years Digit method = Original Value -
Salvage Value) / Sum of Years x Years Remaining
For 2021 = $720000 / 10 x 4 x 3/12 + 720000 / 10 x 3 x 9/12 =
$234000
Double Declining Balance method will result in smallest income
amount.