In a chemostat, the feed flow rate and culture volume are $100$ ml/h and $1.0$ L, respectively. With glucose as substrate, the values of $\mu_{\text{max}}$ and $K_s$ are $0.2 \: h^{-1}$ and $1 \: g/L$, respectively. For a glucose concentration of $10 \: g/L$ in the feed, the effluent substrate concentration (in $g/L$) is _______