5-15. Present value of an annuity Find the present values of these ordinary annuities. Discounting occurs once a year. Round your answers to the nearest cent. a. $600 per year for 12 years at 8%. b. $300 per year for 6 years at 4%. c. $500 per year for 6 years at 0%. d. Rework previous parts assuming that they are annuities due