Answer:
15-ounce package is the best buy.
Explanation:
In order to find the best-buy we have to calculate the price per ounce.
So,
For 7-ounce package:
Price =2.45$
Unit price for 7-ounce:

For 15-ounce Package:
Price: $4.95
Unit price for 15-ounce:

For 26-ounce Package:
Price: $8.84
Unit price for 26-ounce:

As we can see that the least unit price is for 15 ounce pack i.e. 0.33 per ounce so,
15-ounce package is the best buy.