The reaction $AB$ with first order kinetics occur in two reactors connected in series. The fractional conversion in the first and second reactors $($no matter which comes first$)$ is $0\mathrm{.}55$ and $0\mathrm{.}96$ respectively. Which reactor configuration would you recommend for this process?

i$)$ CSTR$\text{'}$s in Series

$($ii$)$ A CSTR followed by a PFR

$($iii$)$ A PFR followed by a CSTR

The molar flow rates into the first and second reactors are $60$ and $45mo\frac{l}{h}r,$ the initial concentration of reactant $A$ is $30mo\frac{l}{m^3}$; the rate constant is $0\mathrm{.}5h{r}^{-1}$