This question guides you to think about the role of credit rating agencies. Sup- pose S&P credit rating is the only thing that determines companies' cost of borrow- ing interest rate on debt). Below is the interest rate associated with each credit rating Credit rating Interest rate AAA AA 3.5% A 4.5% BBB 5.5% BB 7.5% Consider a company that is issuing a ten-year bond with par value $1 billion today. 3% 3 (a) Suppose the company currently has a credit rating of AA. How much inter- est expense can it save over the next ten years if its credit rating become AAA? (b) Suppose the company currently has a credit rating of BBB. How much addi- tional interest expense does it incur over the next ten years if its credit rating drops to BB