Mickey & Minnie have $$39$ million in cash. Before they retire, they want the $$39$ million to grow to $$105$ million. How many years before Mickey & Minnie can retire if they earn $8\mathrm{.}7\%$ per annum on their stash of cash? Assume annual compounding. $($Enter your answer in years to $2$ decimal places, e$.$g$.,12\mathrm{.}34)$

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