A smartphone costing $⁢500 is purchased using a credit card with a 10% annual interest rate. If the full payment is made within the 45 -day grace period, what is the total cost of the smartphone? Formula: total cost=purchase amount+(purchase amount⋅interest rate)

Paying the full balance within the 45-day grace period means no interest is charged. The smartphone therefore costs just its purchase price: $500. The correct choice is 500 dollars; the interest-based choices would apply only if interest were charged.

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