The Heavens Gate Group have $38 million in cash. In order to reach the comet that will take them to a new world they need the $38 million to grow to $81 million. How many years will it take before the group can leave if they earn 6.4% per annum on their stash of cash? Assume annual compounding. (Enter your answer in years to 2 decimal places, e.g., 12.34)