An equimolar mixture of $A$ and $B$ (A being more volatile) is flash distilled continuously at a feed rate of $100 \text{ kmol/h}$, such that the liquid product contains $40\: mol\:\%$ of $A$. If the relative volatility is $6$, then the vapor product, in $\text{kmol/h}$, is
- $10$
- $20$
- $25$
- $45$