Which of the Following Formulas Is Used for Calculating the Equivalent

Which of the following formulas is used for calculating the equivalent fully taxable yield?

A)
$\frac { \text { Taxable Yield } } { 1 -- \text { Marginal Federal Tax Rate } }$
B)
$\frac { \text { Taxable Yield } } { 1 + \text { Marginal Federal Tax Rate } }$
C)
$\frac { \text { Tax Exempt Yield } } { 1 + \text { Marginal Federal Tax Rate } }$
D)
$\frac{\text {Tax Exempt Yield }}{\text {1 - Marginal Federal Tax Rate }}$