Strontium-90 is present in the fallout produced by nuclear weapons testing in the atmosphere. Sr-90 is potentially dangerous to humans and animals because it substitutes chemically for calcium in bones and has a half-life of almost 29 years. What percent of the original amount of Sr-90 remains in a 61 year-old woman who unknowingly drank Sr-90 in contaminated milk when she was 3 years old?