Consider a constant volume bioreactor with continuous operation $($i$.$e$.,$ chemostat$)$ at steady$-$state. Draw a basic scheme of a chemostat. Write a material balance for biomass $($assuming sterile feed and ka $<<$ ja$),$ and show that it is possible to control the growth rate of the cells at a constant value using mechanical devices $($such as valves$).$ Explain the theoretical limit in this control process $($i$.$e$.,$ wash$-$out$).$