Find the present value of the following ordinary annuities (see note to Problem 2-4):
a. $400 per year for 10 years at 10 percent.
b. $200 per year for 5 years at 5 percent.
c. $400 per year for 5 years at 0 percent.
d. Now rework parts a, b, and c assuming that payments are made at the beginning of each year; that is, they are annuities due.