Please explain briefly and show the work

1. A stock has a current price of $20. The risk-free interest rate for a half-year maturity is 6% and the dividend rate is 3%. Assume continuous compounding. What is the six-month forward price of the stock?

2. How many years does it take to double your money if the continuously-compounded interest rate is 6%?

3. If you wanted to double your money in the same time as in the answer to the previous question, but were using monthly compounding, what would be the rate of interest you would require?