Need help with ROI & NPV?

I need some help with ROI (return on investment) and NPV (net present value).

I need to identify the ROI and NPV of the wireless order-tracking system.
Here is the information it gives me:
- The aquisition cost is $35,000 paid at the time of installation.
- It reduces the wait staff by one person: Figure $10 per hour, or 2020 hours per year + 18%
benefits
- Money costs are 7%
- The system may become obsolete in three years

So, I need your help determining the ROI & NPV and determining if the system would be good or not.

Yes, this is my homework question, but I am very confused and need some help.

ROI is calculated by dividing net income attributable to a project by the average assets invested in the project.


ONLY serious answers please and thank you.

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