Need help with c. Need it in excel format, thanks!

Jenco Electric manufactures washdown adjustable speed drives in open loop, encoderless, and closed- loop servo configurations. The net cash flow asso- ciated with one phase of the production operation is shown below. (a) Determine the possible rate of return values according to the rule of signs. (6) Determine the changes of sign in the cumula- tive cash flow series. What does this mean? (c) Write the PW relation to determine i* values. Use the IRR function to display it. Year 0 Net Cash Flow, $ - 40.000 32,000 18,000 1 2 3 - 2000 4 -1000