A hot cup of chai cools at a rate proportional to the temperature difference between the chai and the room. If T is the chai's temperature and T₀ is the room's temperature, the DE is:

A hot cup of chai cools at a rate proportional to the temperature difference between the chai and the room. If T is the chai's temperature and T₀ is the room's temperature, the DE is:

• A. dT/dt = k(T − T₀)
• B. dT/dt = −k(T − T₀)
• C. dT/dt = k(T₀ − T)
• D. Both B and C

Answer: D) Both B and C

Explanation: Newton's Law of Cooling states the rate of cooling is proportional to the temperature difference. dT/dt = −k(T − T₀) where k > 0, which is the same as dT/dt = k(T₀ − T).