What is the present value of the following annuities? a. $2,000 a year for 8 years discounted back to the present at 10 percent. b. $70 a year for 3 years discounted back to the present at 7 percent. c. $300 a year for 12 years discounted back to the present at 11 percent. d. $560 a year for 6 years discounted back to the present at 6 percent