A chemostat with cell recycle is shown in the figure. The feed flow rate and culture volume are $F=75 \mathrm{~L} \mathrm{~h}^{-1}$ and $V=200 \mathrm{~L}$, respectively. The glucose concentration in the feed $\mathrm{C}_{\mathrm{S} 0}=15 \mathrm{~g} \mathrm{~L}^{-1}$. Assume Monod kinetics with specific cell growth rate $\mu_{g}=\frac{1}{\mathrm{C}_{\mathrm{C}}} \frac{d \mathrm{C}_{\mathrm{C}}}{d t}=\frac{\mu_{m} \mathrm{C}_{\mathrm{s}}}{K_{S}+\mathrm{C}_{\mathrm{s}}},$ where $\mu_{m}=0.25 \mathrm{~h}^{-1}$ and $K_{s}=1 \mathrm{~g} \mathrm{~L}^{-1}$. Assume maintenance and death rates to be zero, input feed to be sterile $\left(C_{C_{0}}=0\right)$ and steadystate operation. The glucose concentration in the recycle stream, $\mathrm{C}_{\mathrm{S} 1}$, in $\mathrm{g} \mathrm{L}^{-1}$, rounded off to $1$ decimal place, is $\_\_\_\_\_\_\_\_\_$
