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Use the cash flow given and a MARR = 12% to find the following: a) Determine the number of possible rate of return values in the net cash flow series using the two sign tests. b) Find the rate or rates of return values with excel using interest between -30 and 130% and plot your results. c) Determine the external rate of return, using the modified rate of return approach with an investment rate 5% and a borrowing rate of 7%. Solve the problem using excel. Use the cash flow given and a MARR = 12% to find the following: a) Determine the number of possible rate of return values in the net cash flow series using the two sign tests. b) Find the rate or rates of return values with excel using interest between -30 and 130% and plot your results. c) Determine the external rate of return, using the modified rate of return approach with an investment rate 5% and a borrowing rate of 7%. Solve the problem using excel