Answer:
The 14oz bottle.
Explanation:
Best approach is to find the price per ounce, so that we can compare them on equal terms.
For this, divide each of the prices by the respective volume:
![2.50 / 10 = 0.25 \\ 2.80 / 14 = 0.20 \\ 4.00 / 16 = 0.25 \\ 5.40 / 18 = 0.30](https://img.qammunity.org/2021/formulas/mathematics/high-school/ljffow4wnwhb4scvtuqq78hqcxjprpiqjc.png)
Therefore, we see that the best deal is the 14oz one, having the lowest price per ounce.