Suppose the income tax rate is 0 percent on the first $10,000; 10 percent on the next $20,000; 20 percent on the next $20,000; 30 percent on the next $20,000; and 40 percent on all income above $70,000. Family A has income of $100,000 while Family B has income of $40,000. The marginal tax rates faced by the two families are