What is the Present Value of the following annuities? How did you get to your answer?

a) $3,000 a year for 10 years discounted to the present value at 8%.

b) $50,000 a year for 3 years discounted to the present value at 3%

c) $280 a year for 8 years discounted to the present value at 7%

d) $600 a year for 10 years discounted to the present value at 10%