The Ksp can be used to find the minimum concentration of hydroxide ions required to start the precipitation of Al(OH)3 given a concentration of aluminum ions, and thus determine the pH above which this precipitation occurs. Calculate this pH value if 3.50 lb of aluminum sulfate, Al2(SO4)3, is added to 2150 gallons of water (with a negligible change in volume). Express your answer numerically to two decimal places after the dot.