Applying Gauss' Law: Cylindrical Symmetry

Two large metal plates of area $1.0 {\mathrm{m}}^2$ face each other, $6.0 \mathrm{cm}$ apart, with equal charges of magnitude $\left|q\right|$ but of opposite signs. The field magnitude $E$ between them (neglect fringing) is $72 \mathrm{N} {\mathrm{C}}^{-1}$. Find $\left|q\right|$.

Figure shows a Gaussian surface in the shape of a cube with edge length $5.60 \mathrm{m}$. What are (a) the net flux $\Phi$ through the surface and (b) the net charge $q_{\mathrm{enc}}$ enclosed by the surface if $\overrightarrow{E}=\left(3.00\mathrm{y}\hat{\mathrm{j}}\right) \mathrm{N} {\mathrm{C}}^{-1}$ with $y$ in meters? What are (c) $\varphi$ and (d) $q_{\mathrm{enc}}$ if $\overrightarrow{E}=[-17.0\hat{\mathrm{i}}+\left(6.00+3.00y\right)\hat{\mathrm{j}} ] \mathrm{N} {\mathrm{C}}^{-1}?$