The rate at which an object cools is proportional to the temperature difference between the object and its surroundings, provided that this difference is not too large. The relationship is expressed as a differential equation dy/dt = -k (y - T₀), where T₀ is the temperature of the room, y is the temperature of the object at time t, and k is a constant related to the temperature conductivity of the object.

Suppose there is a 95°C cup of coffe in a 20°C room, and suppose it was observed that coffe cools by 1°C per minute when its temperature is 70°C.
a. Use the information above to find the value of k.