1) The unit rate compares an increase in y with increases in x.
2) To find the unit rate, choose two points. Let's choose (20, 400) and (60, 1200).
3) The unit rate (r) will be the difference in x divided by the difference in y:
![r=(1200-400)/(60-20)](https://img.qammunity.org/2023/formulas/mathematics/college/vbkiiac89g5bs6l1gwlens5g3kr4xv0wpj.png)
4) Now you can find r by solving the division.
![\begin{gathered} r=(800)/(40) \\ r=20 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/9keow43w2196abf153x4khhco0j4cecz6j.png)
Answer: The unit rate is $20/foot.
Alternative C.