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Let C() be the concentration of a drug in the bloodstream As the body eliminates the drug. C() decreases at a rate that is proportional to the amount of the drug that is present at the time. Thus C'() - -KC(1), where & is a positive number called the elimination constant of the drug (a) If Co is the concentration at time / = 0. find the concentration at time I. (b) If the body eliminates half the drug in 30 hours, how long does it take to eliminate 90% of the drug