A stream of pure reactant A $($CA$0=660$ mmole$/$liter$)$ is enter a CSTR at a flow

rate of $540$ mmole$/$min and polymerizes there as follows

$3$A$-----$ R$,$

The above reaction is zero order and rate constant is $54$ mmole$/($liter$.$ min$).$how large a reactor

needed to lower a concentration A in the exit stream to CAf $=330$ mmol$/$liter$.$