In an article about investment alternatives, Money Magazine reported that drug stocks provide a potential for long-term growth, with over fifty percent of the adult-population of the USA taking prescription drugs on a regular basis. For adults 65 and older, 82% take prescription drugs regularly. For adults age 18 to 64, 49% take prescription drugs regularly. The 18-64 group accounts for 83.5% of the adult population (Statistical Abstract of the United Staes, 2008).
a) Given that an adult takes prescription drugs regularly, what is the probability that the adult is 65 or older?