$2$ An irreversible gas$-$phase reaction $A3B$ will be carried out isothermally. The reaction is zero order, the initial concentration of $A$ is $2mo\frac{l}{l}it$ and the system contains $45\%$ inerts. The specific reaction gas constant is $0\mathrm{.}1mo\frac{l}{l}$itmin. Calculate the processing time to achieve $95\%$ conversion in a variable volume batch reactor.