(Compound annuity) What is the accumulated sum of each of the following streams of payments? a. $500 a year for 8 years compounded annually at 11 percent. b. $104 a year for 8 years compounded annually at 8 percent. c. $34 a year for 11 years compounded annually at 12 percent. d. $21 a year for 5 years compounded annually at 4 percent +++