What equal series of payments must be paid into a sinking fund in order to accumulate each given amount?
a) $41,000 in 8 years at 8.24% compounded semiannually when payment is semiannual
b) $25,000 in 15 years at 6.55% compounded quarterly when payments are quarterly
c) $20,000 in six years at 10.85% compounded monthly when payments are monthly.