An investor can design a risky portfolio based on two stocks, C and D. Stock A has an expected return of 22% and a standard deviation of return of 39%. Stock B has an expected return of 14% and a standard deviation of return of 20%. The correlation coefficient between the returns of A and B is -0.6. The risk-free rate of return is 5%. The proportion of the optimal risky portfolio that should be invested in stock B is approximately

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