Kimberly is in the 15% federal marginal tax bracket, so the equivalent taxable yield is 4.41% or 3.75% / (1-.15).

Natalie is in the 28% federal marginal tax bracket, so the equivalent taxable yield is 5.21% or 3.75% / (1 -.28).

Clinton is in the 35% federal marginal tax bracket, so the equivalent taxable yield is 5.77% or 3.75% / (1-.35).

Assuming a corporate bond yields 5.0%, only Kimberly would purchase the corporate bond.