Fluid is flowing over a flat plate. If the surface concentration of a species is 8 mol L^-1 and the concentration in the bulk of the solution is 0.14 mol L^-1, what is the length of the concentration boundary layer (in microns) if the concentration of the species in the boundary layer changes with distance as follows: y = ln(19.9c_A + 1) where y is in units of microns and c_A is in units of mol L^-1 .