In climates with low night-time temperatures, an energy-efficient way of cooling a house's to install a fan in the ceiling that draws air from the interior of the house and discharges it to a ventilated attic space. Consider a house whose interior air volume is720 m°. If air in the house is to be exchanged once every 20 minutes, determine (a) the required flow rate of the fan and (b) the average discharge speed of air if the fan diameter is 0.5 m.

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