Answer:
(a) 22-ounce package
Explanation:
The price per ounce is found by dividing the price by the number of ounces:
6 oz for 1.92 = $1.92/6 = $0.32 /oz
15 oz for $4.95 = $4.95/15 = $0.33 /oz
22 oz for $6.60 = $6.60/22 = $0.30 /oz
The "best buy" in this context is the one that is the least cost per ounce.
The best buy is the 22-ounce package.
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Additional comment
The notion of "best buy" generally assumes a continuous relationship with the product. That is, it assumes you will use the entire package and probably purchase more.
If you only need 3 ounces, spending more than the $1.92 required for a 6-oz package will be a waste of both money and product. For that purpose, the 6-oz package is the "best buy."