In a batch reactor, the dimer $($Substance A$)$ decomposes into two monomers $($Substance B$)$ in an equilibrium reaction. The rate constant $($in s$^-1)$ of the forward reaction $($first order$)$ from Substance A to the monomers B is twice as high as the rate constant $($in L mol$^-1$ s$^-1)$ for the reverse reaction $($second order$)$ of the molecules B to the dimer $($molecule A$).$ At the beginning of the reaction, the concentration of Substance A is $3$ mol$/$L$,$ and monomers are not present at the start of the reaction. Calculate the reaction extent when a reaction volume of $5600$ mL is present.