Consider a two-compartment model of a drug that is inhaled during respiration, as shown in the figure The first compartment (A) corresponds to the airways and alveoli, while the second compartment corresponds to the rest of the body tissue (B). The corresponding volumes are VA and VB. The drug concentration in the airways compartment is C and the concentration in the body tissue is CB. If the concentration in the airways is higher than that in the tissue, the drug is absorbed with an absorption rate constant kA (there is no absorption if the concentration in the tissue is equal or higher than that in the airways, and once the drug has entered the tissue it does not go back to the airways). The drug is eliminated from the tissue with an elimination rate constant kE. The airflow into the airways is approximated with a sinusoidal Q(t) = Asin(2nt/T), where A is the amplitude and T is the breathing period. The drug is delivered into the system at this flow rate with concentration profile Cin(t) injection Cin(t) CA VA air flow (in/out) absorption elimination a) Derive the differential equations for this two-compartment model. Note that the first half of the period corresponds to inspiration (Q>0) and the second half to expiration (Q0) and the second half to expiration (Q