math
posted by aaron .
Hello I am having trouble trying to figure out how to do the last 2 questions in this word problem
In an article about investment growth, Money magazine reported that drug stocks show powerful longterm trends and offer investors unparalleled potential for strong and steady gains. The federal Health Care Financing Administration supports this conclusion through its forecast that annual prescription drug expenditures will reach $366 billion by 2010, up from $117 billion in 2000. Many individuals age 65 and older rely heavily on prescription drugs. For this group, 82% take prescription drugs regularly, 55% take three or more prescriptions regularly, and 40% currently use five or more prescriptions. In contrast, 49% of people under age 65 take prescriptions regularly, with 37% taking three or more prescriptions regularly and 28% using five or more prescriptions (Money, September 2001). The U.S. Census Bureau reports that of the 281,421,906 people in the United States, 34,991,753 are age 65 years and older (U.S. Census Bureau, Census 2000).
questions:
(A) Compute the probability that a person in the United States is age 65 or older (to 2 decimals).
(B) Compute the probability that a person takes prescription drugs regularly (to 2 decimals).
(C) Compute the probability that a person is age 65 or older and takes five or more prescriptions (to 3 decimals).
(D) Given a person uses five or more prescriptions, compute the probability that the person is age 65 or older (to 2 decimals).
correct answers for
(A)".12"
(B)".53"
I don't know how to start solving for question (C) and (D) and I have tried using similar techniques in solving for (A) and (B)
any help is appreciated, thanks in advance!

Answered below