Answer:
1. Depreciation expense for 2019(Straight-line)= (Cost of the assets - Salvage value) / life of the assets
= ($330000 - $33000)/8
= $37,125
2. Sum-of-the-years'-digits = 1+2+3+4+5+6+7+8 = 36
Depreciation Expense for 2019(Sum-of-the-years'-digits method)
= ($330000 - $33000)*8/36
= $66,000
3. Double-declining-balance depreciation rate = (100/8 years)*2 = 25%
Depreciation Expense for 2019 = 330000*25% = $82,500