Answer
$C = 4.55 \times 10^{-11} F $
Work Step by Step
Let ,
$C_{1}=ε_{0}\frac{A}{2}\frac{k_{1}}{2d} =ε_{0}A\frac{k_{1}}{4d}$
$C_{2}=ε_{0}\frac{A}{2}\frac{k_{2}}{d} =ε_{0}A\frac{k_{2}}{2d}$
$C_{3}=ε_{0}A\frac{k_{3}}{2d}$
Note that $C_{2}$ and $C_{3}$ are effectively connected in series, while $C_{1}$ is effectively connected in parallel with the $C_{2} - C_{3}$ combination. Thus,
$C= C_{1} + \frac{C_{2} C_{3}}{C_{2} + C_{3}} = ε_{0}A\frac{k_{1}}{4d} \frac{ε_{0}A\frac{k_{2}}{2d} ε_{0}A\frac{k_{3}}{2d} }{ε_{0}A\frac{k_{2}}{2d} + ε_{0}A\frac{k_{3}}{2d} }$