Three retired couples each require an additional annual income of $2000 per year.As their financial consultant, you recommend that they invest some money in Treasury bills that yield 7%, some money in corporate bonds that yield 9%, and some money in junk bonds that yield 11%. Prepare a table for each couple showing the various ways that their goals can be achieved: 

(a) If the first couple has $20,000 to invest. 

(b) If the second couple has $25,000 to invest. 

(c) If the third couple has $30,000 to invest.