How should I calculate the growth of this investment?

I had one course in accounting and am struggling with doing an opportunity cost graph. The graph involves investments growing in value over 25 years. The first two are easy enough, but I'm uncertain how to handle the third one -- specifically with setting the value of the initial point (year 0). Details: Retail price:$12,900 -- $8,000 in hardware, $4,900 in services Net Cost: $5,900 (after incentives, rebates, etc). Hardware depreciation: assume linear with $2,000 residual value at year 25. Net