In the given circuit, the charge on 4 capacitor will be:

The given circuit can be redrawn as:

Charge on $4\muF$ capacitor:
$Q = \left(\dfrac{4 \times 6}{4 + 6}\right) \times 10$
$Q = 24\mu C$

in series combination charge remains same.

so,

${Q}_{4\muF} = {Q}_{6\muF} = 24\muC$