For workers in closed spaces, it is a great danger to consuming the breathable air (oxygen) and replacing it with carbon dioxide (CO2) is great danger issue. In order to avoid breathing this harmful gas, closed areas should be adequately ventilated. There is no specific standard for the air exchange rate. However, a complete freshening of air every 2.5 minutes has been accepted by the industry as effective ventilation. A worker maintains a rectangular tank with a height of 10 ft and a 5 ft x 5 ft square bottom. Fresh air enters through a 6-inch diameter hose and exits through a 3-inch diameter port on the tank wall. The flow is assumed to be incompressible and steady. Determine, a) The exchange rate required (ft3 /min) for this tank. b) The velocity of the air entering and exiting the tank at this exchange rate.