Charge on a Capacitor

(A)

(a)

(A)

By symmetry we can say that the charge on capacitors C₁ and C₂ will be equal.
Let charge on the left plate of C₁=charge on the right plate of C₂=q.

By conserving the charge on the 3 isolated plates we find that the charge on the upper plate of C₃ = 2q.

Applying KVL in any one of the small loops,

6-qC₁-2qC₃=0

→q = 6μC