$(40$ points$)100$ moles $\frac{?}{h}$ of benzene vapor $(400C,1(atm))$ is mixed with liquid benzene $(20C,1(atm))$ in a well$-$insulated vessel. The singlo stream exiting the vessel is benzene vapor at $200C.$

Determine the flow rate of liquid benzene $($moles$/$h$)$ into the vessel.