3. In the Figure below, $C_1=C_5=8.4\mu F$ and $C_2, C_3$ and $C_4=4.2\mu F$. The applied potential is $V_{ab}=220V$. What is the equivalent capacitance between points a and b?
A) $23.1 \mu F$
B) $25.2 \mu F$
C) $8.4 \mu F$
D) $6.3 \mu F$
E) $2.5 \mu F$