It is desired to distiili a piate column for separating a equimolal feed mixture of A and $B$ to get a product of $95\%$A and $5\%A$ in the distillate and residue respectively. The reflux enters the column at it's bubble point and a reflux ratio of $1\mathrm{.}5$ times the minimum is to be used. Estimate the number of plates needed if the plate efficiency is $80\%.xA00\mathrm{.}160\mathrm{.}310\mathrm{.}490\mathrm{.}661$

$Y_{A}00\mathrm{.}280\mathrm{.}490\mathrm{.}670\mathrm{.}811$