70. To form a buffer solution with pH = 9.0, how many moles of NH4Cl should be added to 3.0 L of 0.20 M NH3(aq) at 25ºC?(Kb of ammonia = 1.8 × 10‒5; assuming the volume of solution does not change after adding NH4Cl)
(A) 0.36
(B) 0.72
(C) 1.08
(D) 3.6
(E) None of the above.