A time-release skin patch releases drug "A" at a constant rate WA( moles/s) into a small volume of skin, Vs. The drug is assumed to be well-mixed in this volume. The drug passes from the skin into the blood stream through a microvascular barrier with permeability-surface area (PAS)s. The drug is removed from the blood stream via excretion at a rate proportional to blood concentration, keCB. Some drug diffuses across the blood-tissue barrier with permeability-surface area (PA)T into the tissue with volume VT (which is also assumed to be well-mixed) where it reacts with tissue components at a rate proportional to tissue concentration kTCT. The partition coefficients for the drug between each compartment are 1.0. (a) Use species mass balances to derive ordinary differential equations for CS,CB, and CT. (b) Provide expressions that can be used to compute these quantities a long time after the patch is in place. Hint: After a long time, we might consider the system to be at steady-state