a b c d

c

Here C , 2C , 3C , 2C and C are in series. Equivalent Capacitance $\frac{1}{C_{eq}} =\frac{1}{C}+\frac{1}{2C}+\frac{1}{3C}+\frac{1}{2C}+\frac{1}{C}= \frac{10}{3C}$ $C_{eq} =\frac{3C}{10}$