Answer:
9.14%
Step-by-step explanation:
Tax exempt yield = 6.40% = 0.064
Marginal tax rate = 30% = 0.30
Equivalent taxable yield = Tax exempt yield / (1 - marginal tax rate)
Equivalent taxable yield = 0.064 / (1 - 0.30)
Equivalent taxable yield = 0.064 / 0.70
Equivalent taxable yield = 0.0914286
Equivalent taxable yield = 9.14%