Answer:
(A) Potential difference between plates will be 6 volt
(b) Initial energy stored will be

Step-by-step explanation:
It is given area of parallel late capacitor

Initial voltage

Distance between plates d = 3 mm = 0.003 m
Capacitance

So charge on the capacitor

(a) This charge will be constant after disconnection.
After disconnection voltage will be

(b) Initial energy stored in the capacitor
