It is necessary to extract 6800 m^3/hr of air at 50ºC and 1 atm from a hot room to the outside of a building through a 50 m long pipe with an external diameter of 500 mm and a thickness of 5 mm. It is made of carbon steel. The air to be extracted is sucked in by a blower located at the line discharge. Calculate the pressure difference between the suction pipe and the blower if, for the system, the total sum of the resistance coefficients of accessories, including the inlet resistance, is k's = 4.2.