\(120 \mathrm{C}_{1}=200 \mathrm{C}_{2} \quad\left[\because C=\frac{q}{v}\right]\)
\(\Rightarrow \quad 3 C_{1}=5 C_{2}\)
$\varepsilon(x)=\varepsilon_{0}+k x, \text { for }\left(0\,<\,x \leq \frac{d}{2}\right)$
$\varepsilon(x)=\varepsilon_{0}+k(d-x)$, for $\left(\frac{d}{2} \leq x \leq d\right)$