113. Solving a chemistry problem

Ionization constants of the tribasic acid H3An: K1 = 1*10-2, K2 = 1*10-6, K3 = 1*10-12. Calculate the pH value at the first and second equivalence points when this acid is titrated with an alkali solution (NaOH). With which indicator is it titrated to a monosubstituted salt and with which indicator to a disubstituted salt? Is direct titration to medium salt possible? What is the pH value at the third equivalence point (at Сsalt = 0.1 M)?