Convince yourself that parts (a), (b) and (c) of figure (31-E13) are identical. Find the capacitance between the points A and B of the assembly.
As the bridge in the balanced form there is no current through 5 μF capacitor
So, C=2.25 μF
Similarly increase of (b)=d (c)
As 'b' can also be written as
Ceq=2.25 μF