I dont need a solution. I just need an explanation for why the costs is negative in the table. When is it negative and when is it positive?

Alt's is contemplating the purchase of a new $218,000 computer-based order entry system. The system will be depreciated straight-line to zero over the system's five-year life. The system will be worth $20,000 at the end of five years. The company will save $73,500 before taxes per year in order processing costs and will initially reduce working capital by $18,600. The net working capital will return to its original level when the project ends. The tax rate is 21 percent. The required return is 9% Answer the following questions: What is the non-discounted cash flow in year 0? What is the non-discounted cash flow in year 1? What is the non-discounted cash flow in year 5? What is the NPV of the project? Will the company accept the project based on NPV? -AC 73,500-73,500-73,500-73.500-73,500 43,600 43.600 43,600 43,600 43,600 29,900 29,900 29,900 29,900 29,900 23621 23621 23621 23621 23621 AEBIT(1-t)