2. Two formations, each 25 m thick, overlie one another. If a constant-velocity vertical flow field is set up across the set of formations with h = 120 m at the top and h = 100 m at the bottom, calculate h at the internal boundary. The hydraulic conductivity of the top formation is 0.0001 m/s and of the bottom formation 0.0010 m/s. Plot head vs. depth. Is the gradient constant, or does it change at the boundary between formations? Why must the gradient be larger in the unit with lower conductivity?