The risky asset has an expected return of 0.22 and a standard deviation of 0.31, and the T-bill has a rate of return of 0.04. What fraction of the portfolio must be invested in the risk-free asset to form a portfolio with a standard deviation of 0.19?

Round your answer to 4 decimal places. For example, if your answer is 3.205%, then please write down 0.0321.