Answer:
depreciable value = $72,000 - $6,000 = $66.000
depreciation expense per unit produced = $66,000 / 500,000 units = $0.132 per unit
depreciation expense year 1 = 90,000 x $0.132 = $11,880
depreciation expense year 2 = 82,000 x $0.132 = $10,824
depreciation expense year 3 = 94,000 x $0.132 = $12,408
Year Depreciation expense Book value
0 $0 $72,000
1 $11,880 $60,120
2 $10,824 $49,296
3 $12,408 $36,888