A rectangular inspection window lies in the $xy$-plane spanning $x=0$ to $L$ and $y=0$ to $W$, with length $L=4.0$ m along $x$ and width $W=1.5$ m along $y$. The electric field is $\vec{E}=\left(\frac{30x}{L}\right)\hat{z}$ N/C, and the surface normal is $+\hat{z}$. Determine the electric flux through the window.