5) A very thick slab has a uniform concentratio of solute A of C0-1x10^-2 mol /m^3 suddenly,the front face of the slab is exposed to a fluid having a concentration of solute A of C1= 0.10 mol/m^3 a) Assuming that the slab is a semi-infinite solid,write down the equation that is cto be solved to determine the concentration profile of solute A, with the boundary and initial conditions. DO NOT solve. b) Calculate the flux in the solid at the surface (x=0) after t-300 s. The diffusion coefficient in the solid is DAB = 4x 10^-9 m^2/s