Newton's law of cooling states that the rate of change of temperature of an object in a surrounding medium (called the ambient temperature) is proportional to the difference between the temperature of the medium and the temperature of the object. suppose a metal bar, initially at temperature 40 degrees celsius, is placed in a room that is held at the constant temperature of 20 degrees celsius. one minute later, the bar has cooled to 22.71 degrees celsius. write the differential equation that models the temperature in the bar t (in degrees celsius) as a function of time t (in minutes).