Consider a plane surface in a uniform electric field as in Figure P 24.45, where $d=15.0 \mathrm{cm}$ and $\theta=70.0^{\circ} .$ If the net flux through the surface is $6.00 \mathrm{N} \cdot \mathrm{m}^{2} / \mathrm{C},$ find the magnitude of the electric field.