The city of Oakmont is interested in developing some lake front property into a sports park$($picnic facilities, boat$$ docks, swimming$$ area, etc.$).$ A consultant has estimated that the city would need to invest $$$ million in this project. In$$ return, the developed property would return $$$ per year to the city through increased tax revenues and recreational benefits to the public. What would the life of this project need to be in order to be$$ cost$-$beneficial to the$$ city? The interest rate on municipal bonds is $\%$ per year.