(Compound annuity) What is the accumulated sum of each of the following streams of payments? a. $500 a year for 10 years compounded annually at 10 percent b. $108 a year for 8 years compounded annually at 8 percent. c. $38 a year for 13 years compounded annually at 12percent. d. $23 a year for 4 years compounded annually at 4 percent