Answer:
 $78,800
Step-by-step explanation:
For computing the net book value at the end of the third year first, we have to determine the depreciation expense that is 
So, under the straight-line method, the depreciation expense would be 
= (Original cost of equipment - residual value) ÷ (useful life) 
= ($174,500 - $15,000) ÷ (5 years) 
= ($159,500) ÷ (5 years) 
= $31,900
The purchase cost is 
= $160,000 + $2,000 + $12,500
= $174,500
For three years, the depreciation would be 
= $31,900 × 3 years 
= $95,700
In this method, the depreciation is same for all the remaining useful life 
Now the book value would be 
= Acquired value of an asset - accumulated depreciation 
= $174,500 - $95,700
= $78,800