Question: (a) A cup of coffee is made with boiling water and stands in a room where the temperature is 20°C. If H(t) is the temperature of the coffee at time t, in minutes, explain what the differential equation
(dH/dt) = -k(H - 20)
says in everyday terms. What is the sign of k?
(b) Solve this differential equation. If the coffee cools to 90°C in 2 minutes, how long will it take to cool to 60°C degrees?