In Fig. $33-66,$ unpolarized light with an intensity of $25 \mathrm{~W} / \mathrm{m}^{2}$ is sent into a system of four polarizing sheets with polarizing directions at angles $\theta_{1}=40^{\circ}, \theta_{2}=20^{\circ}, \theta_{3}=20^{\circ},$ and $\theta_{4}=30^{\circ} .$ What is the intensity of the light that emerges from the system?