What is the present value of the following future amounts?
a. $ 800 to be received 10 years from now discounted back to the present at 10 percent
b. $ 300 to be received 5 years from now discounted back to the present at 5 percent
c. $ 1,000 to be received 8 years from now discounted back to the present at 3 percent
d. $ 1,000 to be received 8 years from now discounted back to the present at 20 percent