You have 500 ml of a solution containing NaCl and NaF, both 0.015 M. both anions can be precipitated by adding Pb(No3)2 to give insoluble lead salts. Ksp for PbCl2 = 1.7*10^-5, ksp for PbF2 = 3.7* 10^-8. how many milligrams of Pb(No3)2 are required to begin precipitation of the less soluble salt?