conductivity and electrochemistry

Exercise 4 Calculate the dissociation constant pK A2 of oxalic acid with PKA = 1.276, if the solution formed by dissolving 0.13 g of its dihydrate in 11 of water shows a conductivity of 41.81 mS-m ? Consider unit activity coefficients and neglect the water conductivity. The limit molar conductivities have the values: 2" (H) = 0.034990 S-m-moll, 2 "(HA) = 0.004306 S-mamol", 2" (A) = 0.014854 S-mmol