Shopping for Soup

Cathy was on a tight budget and was always looking for the most economical buy. While grocery shopping, she saw the following specials on soups:

four 5.5 oz. Cans of Gourmet Soup for $1.28;
twelve 13 oz. Cans of Charlie’s Recipe Soup for $7.08;
ten 5.5 oz. Cans of Zesty Soup for $2.40;
six 13 oz. Cans of Soup Cuisine for $3.75.

Which was the best buy?

Extension
If you were the store owner, how much would you charge for three 32 oz cans of Lou’s Finest soup? Explain.