Arthur sent a chain letter to his friends, asking them to forward the letter to more friends. The relationship between the elapsed time $t$, in months, since Arthur sent the letter, and the number of people, $P(t)$, who receive the email is modeled by the following function: ###$P(t)=12\cdot 5\^{\Large \frac{t}{3.6}}$ **Complete the following sentence about the growth rate of people who receive the email.** The number of people who receive the email grows by a factor of $5$ every [[☃ numeric-input 1]] months.