Norma is in the 32% marginal tax bracket. Because of her high tax rate, Norma is trying to decide if she should renew a certificate of deposit ("CD") of $10,000, 6%, which generates taxable income. Norma could move the $10,000 to tax-exempt municipal bonds. What is the minimum rate of interest Norma would have to receive to make the tax exempt-bond as profitable of an investment as the CD?

4.1%

6.0%

8.4%

9.0%