The correct answer is 400 - 500. The milk nutrient are passed from capillary to alveolar cells. The alveolar cells pass nutrient to lumen of alveoli when alveoli is full the basket cell under the influence of oxytocin contract and milk goes to duct and then to the cistern. When 500 ml blood passes through udder then 1 ml milk is formed. The cows are milked at 12 hour interval.