Calculate ROI and NPV. The acquisition cost is $35,000 paid at the time of installation

The acquisition cost is $35,000 paid at the time of installation. It reduces the wait staff by one person: 10 per hour, or 2020 hours per year + 18% benefits (For this I came up with a total of 23,836)-not sure if correct Money costs are 7% The system may become obsolete in three year. Calculate ROI and NPV.