You can purchase an optical scanner today for $400. The scanner provides benefits worth $60 a year. The expected life of the scanner is 10 years. Scanners are expected to decrease in price by 20% per year. Suppose the discount rate is 10%. When is the best time to purchase the scanner? (Round your answer to the nearest cent.) NPV is maximized when you wait (Click to select) years to purchase the scanner. At this date NPV will be equivalent to $ today.