In the last video, we established that if we say the rate of change of a population with respect to time is going to be proportional to the population, we were able to solve that differential equation and find a general solution which involves an exponential, that the population is going to be equal to some constant times e to some other constant times time. In the last video, we assumed time was days. So let's just apply this just to feel good that we can truly model population in this way. So let's use it with some concrete numbers. And once again, you've probably done that before. You probably started with the assumption that you can model with an exponential function and then you use some information, some conditions, to figure out what the constants are. We probably did this earlier in pre-calculus or algebra class.