Of the following choices, which one is the correct formula for computing the present value (PV) of $1 to be received two years from today at a discount rate of 7 percent?
a) 1 / (1 + 0.07)²
b) 1 / (1 - 0.07)²
c) 1 / (1 + 0.07)⁻²
d) 1 / (1 - 0.07)⁻²