Given that the population quadruples every 39 minutes, you can determine that this bacteria population has Exponential Growth.
By definition, an Exponential Equation as this form:
Where "a" is the initial amount, "b" is the base, and "t" is the time period.
In this case, you know that:
Therefore, since you need to express the time "t" in minutes:
Now you can write the following equation to model the situation: