Use the Following Information to Answer the Question(s)below

Multiple Choice

Use the following information to answer the question(s) below.
Luther Industries has 25 million shares outstanding trading at $18 per share.In addition,Luther has $150 million in outstanding debt.Suppose Luther's equity cost of capital is 13%,its debt cost of capital is 7%,and the corporate tax rate is 21%.
-Luther's after-tax debt cost of capital is closest to:

A) 4.2%.
B) 5.5%.
C) 7.0%.
D) 9.8%.