Sarah makes $3000 contributions at the end of each half-year to a retirement account for 8 years. For the next 20 years, she makes no additional contributions and no withdrawals. If the account earns 7.5%, compounded semi-annually, find the value of the account after the 28 years. (b) If the above account is used to set up an annuity that pays her an amount at the beginning of each 6-month period for the next 20 years, how much will each payment be?