Problem: Diffusion of solid component A into B occurs at room temperature. At time t =0, we connected these two substances (i.e. no diffusion occurs). After 4 h, we found that the component A diffused into B at room temperature, and the concentration of A is 1.09% at the distance of 0.1 mm from the interface. (a) Determine diffusivity of A [unit: m2/h] (b) What will be the concentration at the same position after 23 h?