A cup of coffee is made with boiling water at 100 and stands in
a room where the temperature is 25. The change in temperature, H in
degrees , with respect to time t, in minutes, is given by the
following differential equation. (dH)/(dt)=-k(H-25) Solve this
differential equation. If the coffee cools to 90 in 3 minutes, how
long will it take to cool to 60 degrees? Round your answer to the
nearest integer.