Use Newton's Law of Cooling.
A hot bowl of soup is served at a dinner party. It starts to cool according to Newton's Law of Cooling, so its temperature at time $t$ is given by
$$ T(t)=65+145 e^{-0.05 t} $$
where $t$ is measured in minutes and $t$ is measured in "F.
a. What is the initial temperature of the soup?
b. What is the temperature after $10 \mathrm{min}$ ?
c. After how long will the temperature be $100^{\circ} \mathrm{F}$ ?