8. (Ch. 6) A young Metro graduates decides to start his retirement contributions early, by contributing $4,000 at the end of each half-year into an retirement account. However, life happens and he stops after 8 years of payments (so 16 payments total). For the next 20 years he makes no additional contributions, but also no withdrawals. (a) If the account earns a conservative 7.5%, compunded semiannually, find the value of the account after 28 years. (b) If our graduate's retirement account is used to set up an ordinary annuity that pays him a set amount, at the end of each month, for the next 20 years of his life, how much will each payment be