tO RENT A DVD, a customer must pay $3.99 plus .99 every day that is late. Write rule in function notation

$${f}{\left({\mathtt{r}}\right)} = {\mathtt{3.99}}{\mathtt{\,\small\textbf+\,}}{\mathtt{0.99}}{\mathtt{\,\times\,}}{\mathtt{r}}$$

I used r for days late

The idea behind this formula is simple. The 3.99 is the amount you MUST pay up front.

The "r" multiplied by 0.99 cents to get the late fee.

When you add these two equations together, you get the formula

You plug in the number of days late for "r"