Arock is going to be analyzed for its radioactive isotope contents, x and y. x is the parent and y is the daughter isotope. assume that the half-life of the radioactive isotopes is 1,000,000 years. based on this information, answer the following two questions. a) how much of the parent (x) and how much of the daughter (y) will be present at the time the rock forms? choose one of the following (4 points) and explain why (8 points). total: 12 points. a) x = 100 % ; y = 100 % b) x = 0 % ; y = 100 % c) x = 100 % ; y = 0 % d) x = 50 % ; y = 50 %