Chapter 4.2, Problem 66E

Temperature Wien an object is removed from a furnace and placed in an environment with a constant temperature of ${90}^{\circ }\text{F}$. its core temperature is ${1500}^{\circ }$ Five hours later, the core temperature is ${390}^{\circ }\text{F}$, Explain why there must exist a time in the interval (0, 5) when the temperature is decreasing at a rate of ${222}^{\circ }\text{F}$ per hour.