A stirred$-$tank bioreactor is $12$m in height and $3$m in diameter. Two Rushton turbines with a diameter of $0\mathrm{.}45$ of the tank diameter are installed. The agitation rate is $100$rpm$.$ The working volume reaches $70\%$ of the tank height a scaled$-$down version using a $200-$L reactor that is geometrically similar. What should be the operating conditions if you are to keep the power$-$per$-$unit volume constant or to keep thet ips peed constant?