Present value) 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 10 percent b. $300 to be received 8 years from now discounted back to the present at 7 percent c. $1,000 to be received 13 years from now discounted back to the present at 3 percent d. $1,200 to be received 4 years from now discounted back to the present at 18 percent