The alveoli in the lungs consist of cells that secrete pulmonary surfactants. The surfactants prevent the coarsening of the alveoli and the possible collapse of the lung. They also help to regulate the sizes of the alveoli during breathing. Two alveoli with different radii are shown in the diagram below: Lung tissue (mostly water) Alveoli air way P external r r Inhalation: Alveoli expand Exhalation: Alveoli shrink a) Assume the alveolar radii are 0.05 and 0.07 mm towards the end of exhalation. Knowing that air flows from high to low pressures, calculate the pressure difference between the alveoli and justify why the smaller alveolus does not collapse. (Assume surface tension of alveolar wall due to surfactant is 25 mN/m) b) Some people, like heavy smokers, lack enough surfactant on the alveolar lining. What is the consequence of not having enough surfactant and why would this be a problem? (The surface tension of water is 71.99 mN/m)