Answer:
The owner buys used books for $1.50 each and resells them for 400% of what he paid for them, which is the same as saying he multiplies the purchase price by 4.
So, the selling price of each used book is:
4 x $1.50 = $6.00
Therefore, the price of a used book in this bookstore is $6.00.
The answer is (J) $6.00.
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