#4. (10 points) The time dependent change in the concentration of drug-receptor complex on the cell surface in a human neutrophil (a white blood cell) can be written as: d[DR.] dt = k,[D][R,] - (k, + k.)[DR. ] Where [DR,] is the concentration of Drug-Receptor complex on the cell surface, [D] is the concentration of drug, [R,] is the concentration of surface receptor, and the k's are various rate constants. (a) What is the left-hand side of the solution to this model of drug-receptor binding? (b) Label the axes of the plot of the solution