A woman invests $1,300 at a rate of 8%. Find the time in years that it takes her investment to double with annual compounding (a) using the future value formula and (b) using the Rule of 72. a) Based on the future value formula, it will take approximately years for her investment to double. (Round to two decimal places as needed.) b) Based on the Rule of 72 , it will take approximately years for her investment to double. (Round to two decimal places as needed.)