Ne of the problems of in-air testing of nuclear weapons (or, even worse, the use of such weapons! ) is the danger of radioactive fallout. one of the most problematic nuclides in such fallout is strontium-90 (90sr), which breaks down by β− decay with a half-life of 28 years. it is chemically similar to calcium and therefore can be incorporated into bones and teeth, where, due to its rather long half-life, it remains for years as an internal source of radiation. part a what is the daughter nucleus of the 90sr decay? what is the daughter nucleus of the decay? 9039y 8537rb 8436kr request answer part b what percent of the original level of 90sr is left after 56 years? nothing % % request answer part c how long would you have to wait for the original level to be reduced to 6.25{\rm %} of its original value?