A reactor is to be designed in which the oxidation of cyanide $(CN-)$ to cyanate $(CNO-)$ is to occur by the following reaction,

$0\mathrm{.}5O_2+C{N}^{-}CN{O}^{-}$

The reactor is to be a tank that is vigorously stirred so that its contents are completely mixed, and into and out of which there is a constant flow of waste and treated effluent, respectively. The feed stream flow rate is $43\mathrm{.}8\frac{L}{sec}$ and contains $15,000m\frac{g}{L}CN-.$ The desired reactor effluent concentration is $10m\frac{g}{L}CN.$ Assume that oxygen is in excess, and that the reaction is directly proportional to the cyanide concentration, with a rate constant of $k=0\mathrm{.}5se{c}^{-1}.$ Determine the volume of reactor required to achieve the desired treatment objective, if the reactor behaves as

a$)$ an ideal PFR$,$

b$)$ an ideal CSTR$,$ or

c$)$ a system consisting of $2$ equal size ideal CSTRs connected in$-$series.