Interested

The second question.
This is the topic covered on Page124 Vol.4. Corporate Finance & Portfolio Management.
The basic formula is
Effective Cost of Short-term borrowing = (Interest+Dealer's Commission+Backup Costs)/(Loan amount-Interest).

I found an easier way to do it and it's very effective.
The formula is: {[(Interest rate+Commission Rate+Backup Cost Rate)/12]/(1-Interest rate/12)}*12
The formula can apply to any kind of this type problem. It looks complicated. But it's really easy to be memorized. For example, in the second question you posted,
={[(.0588+.00125+.0025)/12]/(1-.0588/12)}*12=.06286 =>6.29%

Remember,
1. Divide the rates by 100 to convert to decimal numbers.
2. It's 12 there because the question is "monthly". If it's quarterly, divide by 4. Semiannually, divide by2.
3. The last "12" at the end means to annualized.
That's all I know. Good luck on your exam, everyone!