Answer: Mrginal tax rate family A = 16.67%, Family B = 13%
Step-by-step explanation:
Family A income is $30000
Marginal Tax Rate = Total Change in taxes/income
taxes paid = 10000 x 0% + 20000 x 20% + 10000 x 30%
taxes paid = 0 + 2000 + 3000 = 5000
Marginal Tax Rate = 5000/30000 = 0.166666 = 16.67
Family B income is $100000
taxes paid = 10000 x 0% + 20000 x 20% + 10000 x 30% + *20000 x 40%
taxes paid = 0 + 2000 + 3000 + 8000 = 13000
Marginal Tax Rate = 13000/100000 = 13%
*100000 exceeds 80000 by 20000