P5II . 3. It is desired to determine the diffusion flux j= DdC/dx at the surface of a reservoir (x=0). Concentration measurements have been collected as summarized below. If the diffusion coefficient is D=1104m2/s, estimate j. \begin{tabular}{|l|l|l|l|} C(mol/m3) & 15.5 & 12.3 & 6.1 \\ \hline \end{tabular}