A room has a volume of 160 m3. An air-conditioning system is to replace the air in this room every 21.3 minutes, using ducts that have a square cross section. Assuming that air can be treated as an incompressible fluid, find the length of a side of the square if the air speed within the ducts is (a) 3.00 m/s and (b) 6.00 m/s.