$\begin{array}{1 1} \text{(a)$C=\frac{\in_0A}{d}$ } \\ \text{(b)$C=\frac{\in_0d}{A}$} \\ \text{(c)$C=\frac{A}{\in_0d}$ } \\\text{(d)$C=\frac{d}{\in_0A}$ }\end{array} $
