A company that makes clutch disks for race cars has the annual net cash flows shown for one department. (a) Determine the number of positive roots to the rate of return relation. (b) Calculate the internal rate of return. Is there a negative root? How is it treated? (c) Calculate the external rate of return using the return on invested capital (ROIC) approach with an investment rate of 15% per year (as assigned by your instructor, solve by hand and/or spreadsheet)