Total for the 20x40x2 sateen cases with zippers along the longest side is $43.30 each. New total for 6 is $259.80 plus $12 for shipping will be $271.80
With you returning 4 cases (that were $19.67) you will have a credit of $78.68. Applying that credit to the $271.80 total your final balance owed is $193.12.
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San Francisco, CA 94115