Dora bought a bottle of nail polish that was marked down by 20 percent from its original price of 4 point 5 0 dollars Including a 9 percent sales tax, what is the final cost of the bottle of nail polish?

A 20% markdown means Dora pays 80% of the original $4.50 price: $4.50 × 0.80 = $3.60. The 9% sales tax is $3.60 × 0.09 = $0.324, so the total is $3.924, which rounds to $3.92. The final cost is $3.92, choice D.

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