As shown in figures, three identical polaroids $P_1, P_2$ and $P_3$ are placed one after another. The pass axis of $P_2$ and $P_3$ are inclined at angle of $60^{\circ}$ and $90^{\circ}$ with respect to axis of $P_1$. The source $S$ has an intensity of $256 \frac{\mathrm{~W}}{\mathrm{~m}^2}$. The intensity of light at point