Progressive tax brackets determine average and marginal rates Steps:

• Tax on first $20,000 at 15$20,000 × 0.15 = $3,000.
• Additional $10,000 falls in next bracket at 20$10,000 × 0.20 = $2,000.
• Total tax paid: $3,000 +$2,000 = $5,000.
• Average tax rate: $5,000 ÷$30,000 ≈ 16%. Why B is correct:
• Average rate uses formula (total tax ÷ total income) × 100 = 16%; marginal rate is bracket rate on additional income beyond $20,000 = 20%. Why the others are wrong:
• A: Marginal rate is 20%, not 16%.
• C: Average rate is 16%, not 20%.
• D: Average rate is 16%, not 20%.

Final answer: B