Answer:
b. 8.225%
Explanation:
In this question, we use the Rate formula which is shown in the spreadsheet.  
The NPER represents the time period.  
Given that,  
Present value = $754.08
Assuming figure - Future value or Face value = $1,000  
PMT = 1,000 × 7.25% ÷ 2 = $36.25
NPER = 9 years × 2 = 18 years
The formula is shown below:  
= Rate(NPER,PMT,-PV,FV,type)  
The present value come in negative  
So, after solving this,  
1. The pretax cost of debt is 11.75%
2. And, the after tax cost of debt would be
= Pretax cost of debt × ( 1 - tax rate)
= 11.75% × ( 1 - 0.30)
= 8.225%