4. During normal breathing, the volume of the lung can be approximated as V(t)=2VT[1+cos(2ft)], where f is the respiration rate. (Again, V is defined relative to the empty state.) The pressure across the lung wall can be represented as a sum of in-phase and out-of-phase components (and a constant): P(t)=P0+P1cos(2ft)+P2sin(2ft) A) Plot a respiration cycle on a PV diagram (or on a V - P diagram, if you prefer) for the case when pressure and volume are purely in phase. Find the average heat generation rate in the lung tissue. B) Plot a respiration cycle for the case when pressure and volume are purely out-of-phase. Again, find the average heat generation rate in the lung tissue. C) Is P2 a positive or a negative quantity? How do you know