calculate Return On Investment $($ROI$)$

$$ Initial Investment: $$30$ million

$$ Annual Energy Sales Revenue: $$6$ million

$$ Operating and Maintenance Costs: $$1\mathrm{.}5$ million per year

$$ Government Subsidy $($annually for $5$ years$)$: $$1$ million

$$ Resale Value After $15$ Years: $$10$ million