Sally earns graduated commission on her sales each month. She earns 6 percent commission on the first 45 dollars comma 000 in sales and 8 percent on anything over that. If Sally had 51 dollars comma 000 in sales this month, how much commission did she earn?

Sally earns 6% on the first $45,000, which is $45,000 × 0.06 = $2,700. The remaining $6,000 ($51,000 − $45,000) earns 8%, or $6,000 × 0.08 = $480. Adding the commissions gives $2,700 + $480 = $3,180, so the correct choice is C, $3,180.

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