(Solving for n with non-annual periods) Approximately how many years would it take for an investment to grow fourfold if it were invested at 18 percent compounded weekly? Assume that you invest $1 today. If you invest $1 at 18 percent compounded weekly, about how many years would it take for your investment to grow fourfold to $4? (Hint: Remember to convert your calculator solution to years.) years (Round to one decimal place.)