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A couple's retirement plan includes an equal semiannual withdrawal from a bank account for 15 years starting from the time of their retirement. The account balance is $80,000 at the beginning of the retirement period, and the interest rate is 8% per year compounded semiannually. At the time of retirement, they plan on using up the money completely in 15 years. (Round all your answers to two decimal places) a. How much can the couple withdraw from the bank account semiannually if each equal withdrawal is made at the end of every half year after retirement? b. How much can the couple withdraw from the bank account semiannually if each equal withdrawal is made at the beginning of every half year after retirement