Problem 19.20

19.20.
We know that the flux through a surface S is given by
$\Phi = \int_{S}\vec{E}\dot d\vec{A}$
For a flat surface with a normal at an angle $\theta$ to the field, we find that this reduces to
$\Phi = EA\cos \theta$
$\Phi = (2 \times 10^{4}N/C)(18 m^{2}) \cos 10{}^{\circ}$
$\Phi = 355 kN \dot m^{2}/C$.