Suppose the government imposes a tax of 10 percent on the first $40,000 of income and 20 percent on all income above $40,000. What are the tax liability and the marginal tax rate for a person whose income is $50,000?a.12 percent and 20 percent, respectivelyb.12 percent and $50,000, respectivelyc.$6,000 and 12 percent, respectivelyd.$6,000 and 20 percent, respectively