In a multiple linear regression model with two predictor variables, $y = \beta_0 + \beta_1 x_1 + \beta_2 x_2 + \epsilon$, the sample correlation between $x_1$ and $x_2$ is exactly zero. The simple linear regressions of $y$ on $x_1$ and $y$ on $x_2$ yield coefficients of determination $R^2_{y,x_1} = 0.30$ and $R^2_{y,x_2} = 0.25$, respectively. What is the value of the multiple $R^2$ when both predictors are included?