Instant coffee is made by adding boiling water (212F) to coffee mix. If the air temperature is

Instant coffee is made by adding boiling water (212ºF) to coffee mix. If the air temperature is 70ºF, Newton’s law of cooling says that after t minutes, the temperature of the coffee will be given by a function of the form f(t) = 70 + Ae^−kt. After cooling for 2 minutes, the coffee is still 15ºF too hot to drink, but 2 minutes later it is just right. What is this “ideal” temperature for drinking?