\(C_1=\frac{6 A \varepsilon_0}{2 d}=\frac{3 A \varepsilon_0}{d}\)
\(C_2=\frac{A \varepsilon_0}{2\left(d-\frac{d}{2}\left(1-\frac{1}{3}\right)-\frac{d}{2}\left(1-\frac{1}{6}\right)\right)}\)
\(C_2=\frac{A \varepsilon_0}{2\left(\frac{d}{6}+\frac{d}{12}\right)}\)
\(C_2=\frac{A \varepsilon_0}{2\left(\frac{d}{4}\right)}\)
\(C_2=\frac{2 A \varepsilon_0}{d}\)
\(C=C_1+C_2=\frac{5 A \varepsilon_0}{d}\)