The country "Macquarica" has a tax rate of 5% on the first $20,000 of a family's taxable income, then 20% on the next $30,000, then 50% on all taxable income above $50,000 and provides a $5,000 tax exemption per family member. Jane's family has three members and earns a total of $60,000 per year. Calculate the family's marginal tax rate. a. 20% b. 10% c. None is correct d. 50% e. 5%