(Solved): Consider steady one-dimensional diffusion through a funnel of varying cross-sections (Figure below) ...

Consider steady one-dimensional diffusion through a funnel of varying cross-sections (Figure below). Unlike a tube of constant cross section, the concentration varies non-linear with distance. (15\%) Neglect the chemical reactions and convention, and derive the following material balance for steady one-dimensional diffusion through a region of varying cross-section $(\mathrm{A}=\mathrm{A}(\mathrm{x}))$ : $\frac{d(JA(x))}{dx}=0$ Integrate this equation and explain briefly what the result indicates.