Henry Cisco is planning to make two deposits: $$25,000$ now and $$30,000$ at the end of year $6.$ He

wants to withdraw $C$ at the end of each year for the first six years and each year for the next six

years. Determine the value of C if the deposits earn $10\%$ interest compounded annually.

At what rate of interest compounded annually will an investment double in five years?