Step 1: Apply Graham's law of effusion.
According to Graham's law,
\[
\frac{r_1}{r_2}
=
\sqrt{\frac{M_2}{M_1}}
\]
Since the time is the same, the volume effused is proportional to the rate of effusion. Thus,
\[
\frac{V_{CH_4}}{V_X}
=
\sqrt{\frac{M_X}{M_{CH_4}}}
\]
Step 2: Substitute the given values.
Given,
\[
M_X=32\ \text{g mol}^{-1}
\]
and for methane,
\[
M_{CH_4}=16\ \text{g mol}^{-1}
\]
Therefore,
\[
\frac{V_{CH_4}}{300}
=
\sqrt{\frac{32}{16}}
\]
\[
=
\sqrt{2}
\]
\[
V_{CH_4}
=
300\times 1.414
\]
\[
=
424.2\ \text{mL}
\]
Step 3: Final conclusion.
Hence,
\[
\boxed{V_{CH_4}\approx 424\ \text{mL}}
\]
Therefore, the correct option is (4).