What is the present worth of the following series of payments?

(a) $5,000 at the end of each six-month period for 12 years at 9% compounded semiannually.

(b) $7,000 at the end of each quarter for 10 years at 8% compounded quarterly.

(c) $3,500 at the end of each month for five years at 6% compounded monthly.