Let $\alpha$ and $\beta$ respectively be the maximum and the minimum values of the function $$ f(\theta)=4\left(\sin ^4\left(\frac{7 \pi}{2}-\theta\right)+\sin ^4(11 \pi+\theta)\right)-2\left(\sin ^6\left(\frac{3 \pi}{2}-\theta\right)+\sin ^6(9 \pi-\theta)\right), \theta \in \mathbf{R} . $$ Then $\alpha+2 \beta$ is equal to: