For a certain drug to have the desired healing effect and be safe, the amount in a person’s system should be between 28 and 32 micrograms. After 4 hours, the amount of a dosage of the drug left in the body is 85% of the original dosage. The doctor prescribes each dosage to deliver 5 micrograms to the body, and the drug to be taken every 4 hours. What type of series could model this situation? Did the doctor prescribe the correct dosage to reach the ideal healing level?