A process projected to have a total depreciable capital, CTDC$,$ of $ $90$ million, with no allocated costs for off$-$site utilities, is to be installed over a $3-$yr period $(1997-1999).$ Just prior to start$-$up$,$ $$40$ million of working capital is required. At $90\%$ of production capacity $($projected for the third and subsequent operating years$),$ sales revenues, S$,$ are projected to be $ $150$ million $/$ yr and the total annual production cost excluding depreciation is projected to be $ $100$ million$/$yr$.$ Also, the plant is projected to operate at $0\mathrm{.}5$ of $90\%$ and $0\mathrm{.}75$ of $90\%$ of capacity during the first and second operating years. Thus during those years, S$=$$ $75$ million $/$ yr and $ $113$ million$/$yr$,$ respectively. Take straight$-$line depreciation at $8\%/$ yr$.$ Using the third operating year as a basic, compute: a$.$ Return on investment $($ROI$)$ b$.$ Payback period $($PBP$).$