Find out equivalent capacitance between A and B. (take each plate Area = A)

Explanation

The modified circuit is

`C_(eq)=(2C)/(3)=(2A in_(0))/(3d)`
Other method : Let charge density as shown

`C_(eq)=(Q)/(V)=(2xA)/(V)`
`V=V_(2)-V_(4)=(V_(2)-V_(3))+(V_(3)-V_(4))=(xd)/(in_(0))+(2xd)/(in_(0))+(3xd)/(in_(0))`
`:. C_(eq)=(2Ax in_(0))/(3xd)=(2Ain_(0))/(3d)=(2C)/(3)`.