Answer
The value of $X_C$ increases.
Work Step by Step
We can find the new capacitance:
$\frac{1}{C} = \frac{1}{24.0~\mu F} + \frac{1}{24.0~\mu F}$
$\frac{1}{C} = \frac{2}{24.0~\mu F}$
$C = 12.0~\mu F$
The original value of $X_C$ was $X_C = 16.6~\Omega$
We can find the new value of $X_C$:
$X_C = \frac{1}{\omega_d~C}$
$X_C = \frac{1}{2\pi~f_d~C}$
$X_C = \frac{1}{(2\pi)~(400~Hz)~(12.0\times 10^{-6}~F)}$
$X_C = 33.2~\Omega$
The value of $X_C$ increases
