Recent advances have led to the development of a computerized vending machine that can grind coffee beans and brew fresh coffee on demand. The computer also makes possible such functions as changing large bills, tracking the age of an item, and moving the oldest stock to the front of the line, thus cutting down on spoilage. With a price tag of $$4,500$ for each unit, Easy Snack has estimated the cash flows in millions of dollars over the products's six$-$year useful life $($see table$).$ If Easy Snack has a MARR $=18\%,$ should it invest? What is the IRR $($Internal Rate of Return$)$ of the investment?

$\backslash$table$[[n,$Net Cash Flow$],[0,-30],[1,9],[2,18],[3,20],[4,18],[5,10],[6,5]]$

YES: $40\mathrm{.}20\%$

NO: $18\%$

YES: $18\%$

YES: $28\mathrm{.}40\%$