A financial institution offers a "double-your-money" savings account in which you will have $2 in 6 years for every dollar you invest today. What stated annual interest rate (assuming semi-annual compounding) does this account offer?

Please specify your answer in decimal terms and round your answer to the nearest thousandth (e.g., enter 12.3 percent as 0.123).

I think the answer is 0.595, but want to double-check.