The temperature of a pie is $440$ degrees Fahrenheit $3$ hours after being removed from the oven. After $8$ hours out of the oven the temperature of the pie is $79$ degrees Fahrenheit. Derive an exponential formula $f(t)$ for the temperature of a pie as a function of time, $t$ in hours. The formula is going to look something like $f(t) = ab^{t}\text{.}$ The pie went from a temperature of $440$ degrees to a lower temperature of $79$ degrees in a time span of hours.