So,
The Charles law states that, at a constant pressure, the initial and final volume and temperature of a gas is described with the following equation:
![(V_1)/(T_1)=(V_2)/(T_2)](https://img.qammunity.org/2023/formulas/chemistry/college/5gmq3hqk5fy8rap0wm44np4h9tbaobke0o.png)
In this question, we're asked to find the value of V2.
Replacing our values:
![\begin{gathered} (3.4L)/(400K)=(V_2)/(300K) \\ \\ V_2=((3.4L)(300K))/(400K) \\ \\ V_2=2.55L \end{gathered}](https://img.qammunity.org/2023/formulas/chemistry/college/8bor6i5e2b8evxlx1wqnj7utm1lggt0ybj.png)
Therefore, the final volume is 2.55L.