A $$7MW$$ hydro turbine working under a head of $$10$$ $$m$$ at a rotational speed of $$125$$ $$rpm$$ is to be designed and developed by conducting model tests in a laboratory. Maximum possible discharge to the model is $$600$$ liters per second at a constant head of $$5m.$$ Determine the minimum scale of the model and its speed if the expected efficiency of the model is $$85\% .$$