# A.4.16.1 Shopping for Cookbooks

- Author:
- Katie Akesson

Lin is comparing the cost of buying cookbooks at different online stores.
Store A sells them at $9 each and offers free shipping.
Store B sells them at $9 each and charges $5 for shipping.
Store C sells them at dollars and charges $5 for shipping.
Store D sells them at dollars and charges *f* dollars for shipping.
1. Write an equation to represent the total cost, * T*, in dollars as a function of

*cookbooks bought at each store.*

**n**2. Write an equation to find the number of books, * n*, that Lin could buy if she spent

*dollars at each store.*

**T**What happened with the output and inputs from question 1 and 2?