(Present value of an annuity) What is the present value of the following annuities? a. $1,600 a year for 10 years discounted back to the present at 11 percent. b. $80 a year for 5 years discounted back to the present at 9 percent. c. $250 a year for 13 years discounted back to the present at 13 percent. d. $520 a year for 4 years discounted back to the present at 6 percent. a. What is the present value of $1,600 a year for 10 years discounted back to the present at 11 percent? (Round to the nearest cent.)