The solubility products of Al(OH)3 and Zn(OH)2 are 8.5 x 10–23 and 1.8 x 10–14 respectively. If NH4OH is added to a solution containing Al3+ and Zn2+ ions, then substance precipitated first is:
(a) Al(OH)3
(b) Zn(OH)2
(c) Both together
(d) None at all.