An existing robot can be kept if exist1, 900 is spent now to upgrade it 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 18% 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. The AW value of the defender is exist (Round to the nearest dollar.)