When a drug such as a pain killer or an antibiotic is introduced into the body, the kidneys work to eliminate the drug. Assume that after an hour, 35 percent of the drug in the body is eliminated. After another hour, 35 percent of the remaining drug is eliminated, and so on. If a person experiences numbness as long as 125 mg of a certain pain killer remain in the body, after how many hours should a patient stop feeling numbness if initially injected with 400 mg of the pain killer? After hours. (Do not round until the final answer. Then round to the nearest whole number as needed.)