When two identical capacitors are charged individually to different potentials and then connected in parallel, after disconnecting from the source ________

Four capacitors marked with capacitances and break down voltages are connected as shown in the figure. The maximum emf of the source so that no capacitor breaks down is$\_\_\_\_\_\_\_$

In the given circuit, if the potential difference between $A$ and $B$ is $80 \mathrm{V},$ then the equivalent capacitance between $A$ and $B$, and the charge on $10 \mu \mathrm{F}$ capacitor respectively, are