Katie's Boutique Has Zero-Coupon Bonds Outstanding That Mature in Four

Katie's Boutique has zero-coupon bonds outstanding that mature in four years. The bonds have a face value of $1,000 and a current market price of $820. What is the company's pre-tax cost of debt?

A) 5.01 %
B) 5.09 %
C) 5.18 %
D) 5.36 %
E) 5.49 %