Variance of a two-component Gaussian mixture

Let $f_1(x)$ be the probability density function of the $N(0,1)$ distribution and $f_2(x)$ be the probability density function of the $N(0,6)$ distribution. Let $Y$ be a random variable with probability density function $$f(x)=0.6\,f_1(x)+0.4\,f_2(x),\quad -\infty<x<\infty.$$ Then $\mathrm{Var}(Y)$ is equal to