The fraction of gas in a container is 0.5, if the total volume of the container is 6 liter, what is the volume of the gas?

Question

$\begin{array}{1 1} (a)\; 2\;liter \\ (b)\; 3\;liter \\ (c)\; 5\;liter \\ (d)\; 6\;liter \end{array}$