g one of the hazards of nuclear explosions is the generation of 90 sr and its subsequent incorporation in place of calcium in bones. this nuclide emits b particles of energy 0.55 mev and has a half-life of 28.1 a (1 a is the si unit 1 annum, for 1 year). suppose 1.00 mg was absorbed by a newborn child. how much will remain after (a) 19 a and (b) 75 a if none is lost metabolically?