Answer:
a. 5.5%
Step-by-step explanation:
The computation of the cost of debt is shown below:
The Total market value is
= $900 + $600
= $1,500
Now
WACC = Cost of equity × Equity market value ÷ Total market value + Cost of debt × Market value of debt ÷ Total market value
13% = 18% × $900 ÷ $1,500 + Cost of debt × $600 ÷ $1,500
13% = 10.80% + Cost of debt × 0.4
Cost of debt = (13% - 10.80%) ÷ 0.4
= 5.5%
Hence, the cost of debt is 5.5%
Therefore the correct option is a.