Answer: $1,500
Step-by-step explanation:
The net book value of the machine on the sale date is $ 4,500.
This is by adding the depreciation for the half year in the sixth year of $ 500.
So the total depreciation is $ 5,500. The net book value is thus $ 4,500 (Cost $ 10,000 minus Total Depreciation $ 5,500).
The gain is Sales Price $ 6,000 minus Net Book Value $ 4,500 is $ 1,500.