The standard half-cell potential for the reaction at 298.15 K. Calculate E for a 0.700-...

The standard half-cell potential for the reaction at 298.15 K. Calculate E for a 0.700-molal solution of for (a) assuming that the a is equal to the molality and (b) using the measured mean ionic activity coefficient for this concentration, . How large is the relative error if the concentrations, rather than the activities, are used?