Using the rule of 72, approximate the following amounts: (a) If the value of land in an area is increasing 6 percent a year, how long will it take for property values to double? (Round your answer to 1 decimal place.) Time period I years (b) If you earn 15 percent on your investments, how long will it take for your money to double? (Round your answer to 1 decimal place.) Time period years (c) At an annual interest rate of 4 percent, how long will it take for your savings to double? (Round your answer to 1 decimal place.) Time period years