(Compound annuity) What is the accumulated sum of each of the following streams of payments?
a. $480 a year for 8 years compounded annually at 10 percent
b. $112 a year for 8 years compounded annually at 9 percent
c. $34 a year for 11 years compounded annually at 11 percent
d. $26 a year for 5 years compounded annually at 6 percent