Zain, a patient in a hospital, receives 0.7 mg of a certain drug intravenously every hour. The drug is eliminated exponentially in such a way that the fraction of drug that remains in Zain’s body after t hours is f(t) = e^−0.2t. If the treatment is continued indefinitely, approximately how much of the drug will remain in Zain’s bloodstream in the long run (as t → ∞)?