What is the present value of the following annuities?

a. $2,400 a year for years discounted back to the present at 10 percent. b. $80 a year for years discounted back to the present at 9 percent. c. $300 a year for years discounted back to the present at 11 percent. d. $430 a year for years discounted back to the present at 5 percent.