Answer:
The net differential decrease in cost for the entire three years is $8750
Explanation:
The benefits from purchasing the new machine includes the receipt of $6,250 salvage value as well as the reduction in variable manufacturing costs by $23,750 for 3 years ($43,750-$20,000).
Also,additional cost needed to acquire the new machine is the purchase price of $68,750,hence the net benefits overall is shown below:
Salvage value            $6,250
cost savings($23,750*3) Â Â $7,1250
Total benefits            $77,500
costs                  ($68,750)
net benefits            $8,750