Answer:
$188.06
Explanation:
The total cost for the film will be the sum of film cost, applicable sales tax, and applicable shipping charges. The film cost will be the product of the number of rolls and the cost per roll.
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camera shop
film cost = (18 rolls) × ($9.95 /roll) = $179.10
sales tax = 0.05 × $179.10 = $8.96
There is no shipping charge associated with the camera shop purchase, so the total cost is ...
camera shop cost = film cost + sales tax = $179.10 +8.96 = $188.06
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mail order
film cost = (18 rolls) × ($9.76 /roll) = $175.50
shipping charge = $15.00
There is no sales tax associated with the mail order, so the total cost is ...
mail order cost = film cost + shipping charge = $175.50 +$15.00 = $190.50
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The price from the camera shop is the better of the two prices. The purchase there would cost you $188.06 for 18 rolls of film.
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Additional comment
The after-tax charge per roll of film at the camera shop is 9.95×1.05 = 10.4475. This is $0.6975 more than the basic charge per roll from the mail order company. In order to get the shipping charge of $15 to be less than $0.6975 per roll, the number of rolls ordered must be more than 15/0.6975 = 21.5.
An order of 22 rolls of film from the mail order company would cost less than from the camera shop. ($229.50 vs. $229.85)