Answer:
The amount of gain should Jacob Inc. record on December 31, 2015 is $5,000
Explanation:
Truck Value = Â $48,000
Annual depreciation = Â ( $48,000 - Â $8,000) / 8 = $40,000 / 8= $5,000
First year (2013) = $40,000 - $5,000 = Â $35,000
Second year (2014) = $35,000 - $5,000 = Â $30,000
Third year (2015)= $30,000 - $5,000 = Â $25,000
Gain  = Sale Value - Truck Value (actual) = $30,000 - $25,000 = $5,000