Many people take a certain pain medication as a preventative measure for heart disease. Suppose a person takes 70 mg of the medication every 12 hr. Assume also that the medication has a half-life of 12 hr; that is, every 12 hr half of the drug in the blood is eliminated. Complete parts a. and b. below. a. Find a recurrence relation for the sequence (d,) that gives the amount of drug in the blood after the nth dose, where d = 70. OA 20, 140. 1 OB. +70 OC. d.1-140 OD. 24-70 b. Using a calculator, determine the limit of the sequence. In the long run, how much drug is in the person's blood? Confirm the result by finding the limit of the sequence directly. Select the correct choice below and, if necessary, fill in the answer box to complete your choice. OA. The limit of the sequence is mg. OB. The limit does not exist