JEE Advanced Model Paper 9 with solutions for online practice

Parallel plate capacitor A of capacitance C is charged to a potential difference V.Another parallel plate capacitor B of capacitance 2C is charged to a potentialdifference. Charging battery is disconnected and two capacitors are connected inparallel such that positive terminal of A is connected to negative terminal of B. Theelectrostatic energy of the combination is now 6CV2 . The potential difference towhich capacitor B is charged initially is x × 0.7 V . The value of ' x ' is _____.