What is the present value of the following future amounts?

a. $600 to be received 10 years from now discounted back to the present at 11 percent

b. $300 to be received 7 years from now discounted back to the present at 9 percent

c. $1,150 to be received 11 years from now discounted back to the present at 4 percent

d. $1,150 to be received 6 years from now discounted back to the present at 18 percent