(i) Calculation of equivalent capacitance
(ii) Calculation of charge and energy stored
(i) Capacitors ${\mathrm{C}}_2,{\mathrm{C}}_3$ and ${\mathrm{C}}_4$ are in parallel
$\therefore {\mathit{C}}_{234}={\mathit{C}}_2+{\mathit{C}}_3+{\mathit{C}}_4$
$\therefore {\mathit{C}}_{234}=6\mathit{\mu }\mathrm{F}$
Capacitors ${\mathit{C}}_1,{\mathit{C}}_{234}$ and ${\mathit{C}}_5$ are in series
$\frac{1}{{\mathit{C}}_{\mathit{e}\mathit{q}}}=\frac{1}{{\mathit{C}}_1}+\frac{1}{{\mathit{C}}_{234}}+\frac{1}{{\mathit{C}}_5}$ $=\frac{1}{2}+\frac{1}{6}+\frac{1}{2}$
$=\frac{7}{6}\mathit{\mu }\mathrm{F}$
${\mathit{C}}_{\mathit{e}\mathit{q}}=\frac{6}{7}\mathit{\mu }\mathrm{F}$
(ii) Charge drawn from the source
$\mathit{Q}={\mathit{C}}_{\mathit{e}\mathit{q}}\mathit{V},$
$=\frac{6}{7}\times 7\mathit{\mu }\mathrm{C}=6\mathit{\mu }\mathrm{C}$
Energy stored
$\mathit{U}=\frac{{\mathit{Q}}^2}{2\mathit{C}}$
$=\frac{6\times 6\times {10}^{-12}\times 7}{2\times 6\times {10}^{-6}}=21\mathit{\mu }\mathrm{J}$