please explain how its done, please and thanks

(Chapter 9): An existing robot can be kept if $2,000 is spent now to upgrade if for future service requirements. Alternatively, the company can purchase a new robot to replace the old robot. The following estimates have been developed for both the defender and the challenger. The company's before-tax MARR is 20% per year. Based on this information, should the existing robot be replaced right now? Assume the robot will be needed for an indefinite period of time. Draw cash flows diagram