An exponential function has the form where and the base is a positive real number other than Let's determine and interpret and of the given model. In this situation, represents the number of subscribers it received at the beginning of the model. Because is greater than and less than it represents the growth factor of the number of referrals each year. To determine the annual percent increase, we should consider the exponential growth model. In the model, is the percent increase written as a decimal and the quantity is the growth factor. Knowing that the growth factor is in our situation, we can find the percent increase.