According to the National Center for Health Statistics, the life expectancy for a 55-year-old American female is 28.9 years. Assuming that, from age 55, the survival of American females follows an exponential distribution, determine the following probabilities.

(a) The probability that a randomly selected 55-year-old American female will live beyond 80 years of age (at least 25 more years)
(b) The probability that a randomly selected 55-year-old American female will live less than 20 more years.