When switch is closed, charge on C₁ is ____ $\mathrm{\mu }$C

Let q₁ and q₂ be the charges on the two capacitor after closing the switch, then

$\frac{{\mathrm{q}}_1}{2}+\frac{{\mathrm{q}}_2}{2}=10\dots (\mathrm{i})\mathrm{and} -{\mathrm{q}}_1-{\mathrm{q}}_2=-20\mathrm{. }$ In series charge on the capacitors is same that is $20 \mathrm{\mu c}$