Need help with this Chem problem.

Between 2014 and 2016, more than 25,000 children in flint, michigan, drank water that was contaminated with lead from lead pipes. during this time, the city claimed the water was safe to drink. which of these actions could the city have taken to ensure that the drinking water was free from lead?

Which of these conditions most likely produces an unstable isotope?

The volume of helium in a blimp is 6.28 x 10^9 millimeters. the density of helium in the blimp is .1786 kilogram/meter^3. find the mass of the helium in the blimp.