Hello, i need help with this chemical engineering problem. Please i need every step explained well for the resolution of the exercise.

A growth factor (K) is released in the extravascular volume which contains a blood vessel which we can consider cylindrical. Under steady state conditions, the concentration of K in this volume is constant and equal to 1 M. The goal is to transport growth factor K into the blood vessel endothelium as it traverses the extra-vascular volume (Figure 1). The outer (R0) and inner (Ri) radius of the blood vessel is 200 and 150 m, respectively. The thickness of the endothelial lining is 1 m. The diffusion coefficient of K through the vessel wall and through the endothelium is 10^-7 (cm^2)/s and 10^-9 (cm^2)/s, respectively. Assume that the concentration of potassium in the blood is negligible.

a) Define the mass balance for growth factor K at the blood vessel wall and the boundary conditions.

b) Define the mass balance for the growth factor K on the volume of the endothelium and the boundary conditions;

c) Determine the mean K concentration in the endothelial volume assuming the conditions stationary.

Figure 1: