You can purchase an optical scanner today for $420. The scanner provides benefits worth $70 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 12%. When is the best time to purchase the scanner? (Round your answer to the nearest cent.)

NPV is maximized when you wait ? years to purchase the scanner.

At this date NPV will be equivalent to $?today.

Find ?