Suppose the tax amount on the first​ $10,000 income is​ $0; $2,000 on the next​ $20,000; $4,000 on the next​ $20,000; $6,000 on the next​ $30,000; and 40 percent on any income over​ $80,000. Family A has income of​ $30,000 and Family B has income of​ $80,000. What is the marginal and average tax rate for each​ family? A. Family​ A: marginal—10 ​percent; average—10 ​percent; Family​ B: marginal—40 ​percent; average—40 percent. B. Family​ A: marginal—10 ​percent; average—6.7 ​percent; Family​ B: marginal—20 ​percent; average—15 percent. C. Family​ A: marginal—10 ​percent; average—15 ​percent; Family​ B: marginal—40 ​percent; average—20 percent. D. Family​ A: marginal—10 ​percent; average—20 ​percent; Family​ B: marginal—30 ​percent; average—23 percent.