Q.Let for $f(x) = 7\tan^{8} x + 7\tan^{6} x - 3\tan^{4} x - 3\tan^{2} x, I_{1} = \int_{0}^{\pi/4} f(x) \, dx$ and $I_{2} = \int_{0}^{\pi/4} x f(x) \, dx.$ Then $7I_{1} + 12I_{2}$ is equal to: