Question $2(3\mathrm{.}0$ mark$)($L$\mathrm{.}0\mathrm{.}1)$

The irreversible and second order reaction $A2R+S$ is carried out in a plug flow reactor. The pressure of feed is $10stm$ at $800K$ and feed stream contains $70\%$ reactant A and $30\%$ inert by volume. The reactor of $0\mathrm{.}2L$ is isothermal, and the reaction occurs at $800K$ and pressure of $10$atm. It is known that the outflow of the product $R$ is $0\mathrm{.}034mo\frac{l}{s}$ and the conversion was $10\%.$ Calculate the reaction rate constant if the reaction rate is $-{}_A=kC{A}_A^2($irreversible reactions at variable volume$).$