A thermos is filled with hot coffee and placed directly outside where the temperature is around zero degrees. The temperature of the coffee decreases exponentially with time. After 4 hours the temperature is 76 °C and at the same time the temperature is decreasing at the rate of 4.1 °C per hour. a) What was the temperature of the coffee when it was poured into the thermos? b) The coffee is considered drinkable as long as its temperature does not fall below 55 °C. How long after pouring the coffee into the thermos is it still drinkable?

A thermos is filled with hot coffee and placed directly outside where the temperature is around zero degrees. The temperature of the coffee decreases exponentially with time. After 4 hours the temperature is 76 °C and at the same time the temperature is decreasing at the rate of 4.1 °C per hour. a) What was the temperature of the coffee when it was poured into the thermos? b) The coffee is considered drinkable as long as its temperature does not fall below 55 °C. How long after pouring the coffee into the thermos is it still drinkable?