6-4 Find the present values of the following ordinary annuities: a. PMT of $400 each year 5 years at a simple rate of 12 percent, compounded annually. b. PMT of $200 each year for 10 years at a simple rate of 12 percent, compounded annually c. The annuities described in parts a and have the same amount of money paid into them and both earn interest at the same simple rate, yet the present value of the annuity in part a is greater than the one in part b. Why does this occur