$7\mathrm{.}27$ The annual revenues $($in $$1000$ units$)$ associated with several large apartment complexes are $$0,$ $$350,$ $$290,$ $$460,$ $$150,$ and $$320$ for years $0,1,2,3,4,$ and $5,$ respectively. Determine $(1)$ whether each cash flow series is conventional or nonconventional, $(2)$ the maximum number of real$-$number roots, and $(3)$ if there is one, positive real$-$number$$i$*$ value. The cash flows for years $0,1,2,3,4,$ and $5,$ respectively, are:

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