Which of the following statements about the future value of a dollar is true?
a. A dollar paid (or received) in the future is worth more than a dollar paid (or received) today.
b. A dollar paid (or received) in the future is worth as much as a dollar paid (or received) today.
c. A dollar paid (or received) in the future is worth less than a dollar paid (or received) today.
d. A dollar paid (or received) in the future is not comparable to a dollar paid (or received) today.