Evaluate the net present value of a stream of income:
a) V = $1, 000 per year at an interest rate of 5% in perpetuity
b) V = $1, 000 per year at an interest rate of 12% in perpetuity
c) V = $1, 000, 000 per year at an interest rate of 10% in perpetuity
d) V = $1, 000, 000 per year in perpetuity, but not beginning until year t at an interest rate of 15%