If the same reaction is performed under unchanged operating condition in the same non$-$ideal CSTR which is modelled by a different scheme wherein the ideal PFR precedes the ideal CSTR$,$ the conversion would be$,$

$55\mathrm{.}3\%$

$63\mathrm{.}4\%$

$74\mathrm{.}5\%$

$90\mathrm{.}7\%$