Calculate the standard deviation of a three-asset portfolio given the following data:

Funds: S&P 500 Intermediate Treasury European

Weights 50% 35% 15%

Mean 17.23% 8.24% 12.47%

Standard deviation 14.04% 8.04% 12.13%

Correlation matrix: S&P 500 Intermediate Treasury European

S&P 500 1.0 0.71 0.47

Intermediate Treasury 0.71 1.0 0.64

European 0.47 0.64 1.0