What annual equal payment series is necessary to repay the following increasing series of payments?
a. A series of 7 end-of-year payments that begins at $2,000 and increases at the rate of $100 a year with 10% interest compounded annually.
b. A series of 30 end-of-year payment that begins at $250 and increases at the rate of $50 a year with 9% interest compounded annually.
c. A series of 25 end-of-year payments that begins at $400 and increases at the rate of $200 a year with 12.5% interest compounded annually.