A simple distillation column separates a binary mixture of $A$ and $B$. The relative volatility of $A$ with respect to $B$ is $2$. The steady-state composition of $A$ in the vapour leaving the $1^{\text {st }}, 2^{\text {nd }}$ and $3^{\text {rd }}$ trays in the rectifying section are $94,90$ and $85 \mathrm{~mol} \%$, respectively. For ideal trays and constant molal overflow, the reflux-to-distillate ratio is
- $1.9$
- $2.7$
- $1.2$
- $1.1$