Silver iodide is sprayed from airplanes by modern “rainmakers” in an attempt to coax rain from promising cloud formations. The silver iodide crystals provide “seeds,” that is, sites for condensation of water. Silver iodide satisfies two requirements needed to form water drops. First, the crystals are quite small, and second, the solubility in water is extremely low. If the solubility of silver iodide in water is 9 × 10^-9 M, calculate K_sp for AgI.