$3)$ Consider simple irreversible liquid phase reaction A$->$ R$.$ A liquid reactant stream $($CA$0=1$ mol$/$liter$)$ passes through two CSTR reactors in a series with a constant volumetric flow rate. The concentration of A in the exit of the first reactor is $0\mathrm{.}5$ mol$/$liter$.$ Reaction constant remains the same for both CSTRs$.$ Find the concentration in the exit stream of the second reactor. The reaction is second$-$order with respect to A and V$2/$V$1=2.$ Hint: try to solve using space time, it has the same relation for two reactors as its volumes.