a. If the interest rate is 6.4% per year, approximately how long will it take for your money to quadruple in value? Note: Use the Rule of 72. Round your answer to 2 decimal places. b. If the inflation rate is 4.2% per year, what will be the change in the purchasing power of your money over this period? Note: Use the Rule of 72 to compute the number of years. Do not round intermediate calculations. Enter your answer as a percent rounded to 2 decimal places