What is the equivalent capacitance of the system of capacitors between $A$ and $B$?

All six capacitors shown are identical. Each can withstand a maximum of $200\, V$ between its terminals. The maximum voltage that can be safely applied between $A$ and $B$ is.....$V$

Two parallel plate capacitors are connected in series. Each capacitor has a plate area $A$ and a separation $d$ between the plates. The dielectric constants of the media between their plates are $2$ and $4$. The separation between the plates of a single air capacitor of plate area $A$ which effectively replaces the combination is:

On each side of a polygon of $n$ sides,a capacitor of capacitance $C$ is placed as shown in the figure. The equivalent capacitance across $A$ and $B$ is:

Three capacitors of capacitance $1\ \mu F$,$2\ \mu F$,and $3\ \mu F$ are connected in series,and a potential difference of $11\ V$ is applied across the combination. The potential difference across the plates of the $1\ \mu F$ capacitor is......$V$.

Two condensers of capacity $0.3\,\mu F$ and $0.6\,\mu F$ respectively are connected in series. The combination is connected across a potential of $6\,V$. The ratio of energies stored by the condensers will be