6-11. (Annuity payments) The Knutson Corporation needs to save $15 million to retire a $15 million mortgage that matures in 10 years. To retire this mortgage, the company plans to put a fixed amount into an account at the end of each year for 10 years. The Knutson Corporation expects to earn 10 percent annually on the money in this ac- count. What equal annual contribution must the firm make to this account to accu- mulate the $15 million by the end of 10 years? 6-12. (Future value of an annuity) Upon graduating from college 35 years ago, Dr. Nick Riviera was already planning for his retirement. Since then, he has made deposits into a retirement fund on a quarterly basis in the amount of $300. Nick has just com- pleted his final payment and is at last ready to retire. His retirement fund has eaned 9 percent compounded quarterly a. How much has Nick accumulated in his retirement account? b. In addition to this, 15 years ago Nick received an inheritance check for $20.000 from his beloved uncle. He decided to deposit the entire amount into his retire- ment fund. What is his current balance in the fund