Reconstruct a question, answer pair from this explanation: The price per kilogram of potatoes is $6 / 2 = $3. To buy 5 kg of potatoes, she will have to pay 5 * $3 = $15.

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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Q:Daphney buys 5 kg of potatoes at the supermarket. If 2 kg of potatoes costs $6, how much will she pay?
A:15